X509UtilTest#testClientRenegotiationFails is flaky on JDK8 + linux on machines with 2 cores

On this Fedora machine:
[eolivelli@localhost zookeeper-server]$ uname -a
Linux localhost.localdomain 5.2.9-200.fc30.x86_64 #1 SMP Fri Aug 16 21:37:45 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

[eolivelli@localhost zookeeper-server]$ mvn -v
Apache Maven 3.6.2 (40f52333136460af0dc0d7232c0dc0bcf0d9e117; 2019-08-27T17:06:16+02:00)
Maven home: /home/eolivelli/Scaricati/maven
Java version: 1.8.0_222, vendor: AdoptOpenJDK, runtime: /home/eolivelli/dev/jdk8u222-b10/jre
Default locale: it_IT, platform encoding: UTF-8
OS name: "linux", version: "5.2.9-200.fc30.x86_64", arch: "amd64", family: "unix"

[eolivelli@localhost zookeeper-server]$ cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 21
model : 112
model name : AMD A9-9410 RADEON R5, 5 COMPUTE CORES 2C+3G
stepping : 0
microcode : 0x6006704
cpu MHz : 1444.800
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
apicid : 16
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good acc_power nopl nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm perfctr_core perfctr_nb bpext ptsc mwaitx cpb hw_pstate ssbd vmmcall fsgsbase bmi1 avx2 smep bmi2 xsaveopt arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif overflow_recov
bugs : fxsave_leak sysret_ss_attrs null_seg spectre_v1 spectre_v2 spec_store_bypass
bogomips : 5789.50
TLB size : 1536 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro acc_power [13]

processor : 1
vendor_id : AuthenticAMD
cpu family : 21
model : 112
model name : AMD A9-9410 RADEON R5, 5 COMPUTE CORES 2C+3G
stepping : 0
microcode : 0x6006704
cpu MHz : 1483.889
cache size : 1024 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
apicid : 17
initial apicid : 1
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good acc_power nopl nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm perfctr_core perfctr_nb bpext ptsc mwaitx cpb hw_pstate ssbd vmmcall fsgsbase bmi1 avx2 smep bmi2 xsaveopt arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif overflow_recov
bugs : fxsave_leak sysret_ss_attrs null_seg spectre_v1 spectre_v2 spec_store_bypass
bogomips : 5789.50
TLB size : 1536 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro acc_power [13]

[INFO] Running org.apache.zookeeper.common.X509UtilTest
[ERROR] Tests run: 336, Failures: 0, Errors: 4, Skipped: 0, Time elapsed: 12.382 s <<< FAILURE! - in org.apache.zookeeper.common.X509UtilTest
[ERROR] testClientRenegotiationFails[1](org.apache.zookeeper.common.X509UtilTest) Time elapsed: 0.103 s <<< ERROR!
java.lang.Exception: Unexpected exception, expected<javax.net.ssl.SSLHandshakeException> but was<java.lang.AssertionError>
at org.apache.zookeeper.common.X509UtilTest.testClientRenegotiationFails(X509UtilTest.java:575)

[ERROR] testClientRenegotiationFails[4](org.apache.zookeeper.common.X509UtilTest) Time elapsed: 0.064 s <<< ERROR!
java.lang.Exception: Unexpected exception, expected<javax.net.ssl.SSLHandshakeException> but was<java.lang.AssertionError>
at org.apache.zookeeper.common.X509UtilTest.testClientRenegotiationFails(X509UtilTest.java:575)

I see this test failing very often:

[ERROR] testClientRenegotiationFails[6](org.apache.zookeeper.common.X509UtilTest) Time elapsed: 0.046 s <<< ERROR!
java.lang.Exception: Unexpected exception, expected<javax.net.ssl.SSLHandshakeException> but was<java.lang.AssertionError>
at org.apache.zookeeper.common.X509UtilTest.testClientRenegotiationFails(X509UtilTest.java:575)

[ERROR] testClientRenegotiationFails[7](org.apache.zookeeper.common.X509UtilTest) Time elapsed: 0.06 s <<< ERROR!
java.lang.Exception: Unexpected exception, expected<javax.net.ssl.SSLHandshakeException> but was<java.lang.AssertionError>
at org.apache.zookeeper.common.X509UtilTest.testClientRenegotiationFails(X509UtilTest.java:575)