SimpleMockNioTransportTests.testConnectException fails on MacOS

[tvernum]

This seems to be triggered by #32560 (reverting 0cf0d73 solves the problem)

https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+multijob-darwin-compatibility/11/console

REPRODUCE WITH: ./gradlew :test:framework:test -Dtests.seed=9C3DC2779BDE41C3 -Dtests.class=org.elasticsearch.transport.nio.SimpleMockNioTransportTests -Dtests.method="testConnectException" -Dtests.security.manager=true -Dtests.locale=ar-LB -Dtests.timezone=America/Anchorage -Dcompiler.java=10 -Druntime.java=8

02:08:43   1> [2018-09-19T18:08:40,751][INFO ][o.e.t.t.MockTransportService] [testConnectException] publish_address {127.0.0.1:49748}, bound_addresses {[::1]:49747}, {127.0.0.1:49748}
02:08:43   1> [2018-09-19T18:08:40,773][INFO ][o.e.t.n.SimpleMockNioTransportTests] [testConnectException] after test
02:08:43 FAILURE 0.06s J3 | SimpleMockNioTransportTests.testConnectException <<< FAILURES!
02:08:43    > Throwable #1: java.lang.AssertionError: 
02:08:43    > Expected: a string containing "connect_exception"
02:08:43    >      but: was "[][127.0.0.1:9876] general node connection failure"
02:08:43    > 	at __randomizedtesting.SeedInfo.seed([9C3DC2779BDE41C3:78B03D75C4C593DD]:0)
02:08:43    > 	at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
02:08:43    > 	at org.elasticsearch.transport.nio.SimpleMockNioTransportTests.testConnectException(SimpleMockNioTransportTests.java:107)
02:08:43    > 	at java.lang.Thread.run(Thread.java:748)
02:08:43   1> [2018-09-19T18:08:40,793][INFO ][o.e.t.n.SimpleMockNioTransportTests] [testErrorMessage] before test

Reproduces for me Darwin Kernel Version 16.7.0: Fri Apr 27 17:59:46 PDT 2018; root:xnu-3789.73.13~1/RELEASE_X86_64

CC: @tbrooks8

[elasticmachine]

Pinging @elastic/es-core-infra

[tvernum]

I muted this test on MacOS - ff934e3

[original-brownbear]

@tvernum sorry about that, reproducing and fixing on OSX right away :)