libprocess tests breaking on macOS.

[----------] 8 tests from HTTPConnectionTest
[ RUN      ] HTTPConnectionTest.GzipRequestBody
../../../3rdparty/libprocess/src/tests/http_tests.cpp:972: Failure
Failed to wait 15secs for connect
[  FAILED  ] HTTPConnectionTest.GzipRequestBody (15001 ms)
[ RUN      ] HTTPConnectionTest.Serial
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1015: Failure
(connect).failure(): Failed to connect to 192.168.178.20:51437: Host is down
[  FAILED  ] HTTPConnectionTest.Serial (0 ms)
[ RUN      ] HTTPConnectionTest.Pipeline
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1094: Failure
(connect).failure(): Failed to connect to 192.168.178.20:51437: Host is down
[  FAILED  ] HTTPConnectionTest.Pipeline (1 ms)
[ RUN      ] HTTPConnectionTest.ClosingRequest
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1190: Failure
(connect).failure(): Failed to connect to 192.168.178.20:51437: Host is down
[  FAILED  ] HTTPConnectionTest.ClosingRequest (0 ms)
[ RUN      ] HTTPConnectionTest.ClosingResponse
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1245: Failure
(connect).failure(): Failed to connect to 192.168.178.20:51437: Host is down
[  FAILED  ] HTTPConnectionTest.ClosingResponse (0 ms)
[ RUN      ] HTTPConnectionTest.ReferenceCounting
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1306: Failure
(*connect).failure(): Failed to connect to 192.168.178.20:51437: Host is down
[  FAILED  ] HTTPConnectionTest.ReferenceCounting (1 ms)
[ RUN      ] HTTPConnectionTest.Equality
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1333: Failure
(connect).failure(): Failed to connect to 192.168.178.20:51437: Host is down
[  FAILED  ] HTTPConnectionTest.Equality (0 ms)
[ RUN      ] HTTPConnectionTest.RequestStreaming
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1360: Failure
(connect).failure(): Failed to connect to 192.168.178.20:51437: Host is down
[  FAILED  ] HTTPConnectionTest.RequestStreaming (0 ms)
[----------] 8 tests from HTTPConnectionTest (15003 ms total)

[----------] 8 tests from HttpAuthenticationTest
[ RUN      ] HttpAuthenticationTest.NoAuthenticator
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1792: Failure
(response).failure(): Failed to connect to 192.168.178.20:51437: Host is down
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1786: Failure
Actual function call count doesn't match EXPECT_CALL(*http.process, authenticated(_, Option<Principal>::none()))...
         Expected: to be called once
           Actual: never called - unsatisfied and active
[  FAILED  ] HttpAuthenticationTest.NoAuthenticator (1 ms)
[ RUN      ] HttpAuthenticationTest.Unauthorized
../../../3rdparty/libprocess/src/tests/http_tests.cpp:1816: Failure
(response).failure(): Failed to connect to 192.168.178.20:51437: Host is down
WARNING: Logging before InitGoogleLogging() is written to STDERR
F0921 12:18:19.947710 2519827264 future.hpp:1151] Check failed: !isFailed() Future::get() but state == FAILED: Failed to connect to 192.168.178.20:51437: Host is down
*** Check failure stack trace: ***
*** Aborted at 1505989099 (unix time) try "date -d @1505989099" if you are using GNU date ***
PC: @     0x7fff5cd45fce __pthread_kill
*** SIGABRT (@0x7fff5cd45fce) received by PID 23916 (TID 0x7fff96318340) stack trace: ***
    @     0x7fff5ce76f5a _sigtramp
    @     0x7fff5ac5e526 std::__1::locale::facet::__on_zero_shared()
    @     0x7fff5cca232a abort
    @        0x1077b9659 google::logging_fail()
    @        0x1077b964a google::LogMessage::Fail()
    @        0x1077b72fc google::LogMessage::SendToLog()
    @        0x1077b8089 google::LogMessage::Flush()
    @        0x1077c12e9 google::LogMessageFatal::~LogMessageFatal()
    @        0x1077b9b35 google::LogMessageFatal::~LogMessageFatal()
    @        0x106998ad1 process::Future<>::get()
    @        0x1069d4d5b HttpAuthenticationTest_Unauthorized_Test::TestBody()
    @        0x1070a828e testing::internal::HandleSehExceptionsInMethodIfSupported<>()
    @        0x10704a96b testing::internal::HandleExceptionsInMethodIfSupported<>()
    @        0x10704a896 testing::Test::Run()
    @        0x10704c60d testing::TestInfo::Run()
    @        0x10704dc0c testing::TestCase::Run()
    @        0x10705e14c testing::internal::UnitTestImpl::RunAllTests()
    @        0x1070ac2fe testing::internal::HandleSehExceptionsInMethodIfSupported<>()
    @        0x10705db7b testing::internal::HandleExceptionsInMethodIfSupported<>()
    @        0x10705da48 testing::UnitTest::Run()
    @        0x106c21181 RUN_ALL_TESTS()
    @        0x106c20cc4 main
    @     0x7fff5cbf6145 start
    @                0x1 (unknown)