impalad failed to start due to JDWP error

A custom cluster test in a downstream environment failed to start one of its impalad:

Picked up JAVA_TOOL_OPTIONS: -agentlib:jdwp=transport=dt_socket,address=30000,server=y,suspend=n
ERROR: transport error 202: bind failed: Address already in use
ERROR: JDWP Transport dt_socket failed to initialize, TRANSPORT_INIT(510)
JDWP exit error AGENT_ERROR_TRANSPORT_INIT(197): No transports initialized [debugInit.c:750]
Wrote minidump to /data/jenkins/workspace/impala-asf-master-core-asan/repos/Impala/logs/custom_cluster_tests/minidumps/impalad/112be12c-25f0-426c-a4fa998f-020a4c4e.dmp

Looks like something else was using port 30000, perhaps a previous impalad wasn't released properly. Very difficult to know. This bug is just to track any other occurrences. lv helped me look at this and we questioned whether CI runs need to have this enabled in the first place: this is likely only useful in a CI environment if a live hang is noticed, which is infrequent and unlikely. In my opinion this can be low priority unless this starts to affect builds.