[Java] Java tests fail non-deterministically with memory leak from Flight tests

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see eg https://travis-ci.org/apache/arrow/jobs/434044723

Starting server.
[ERROR] Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.129 s <<< FAILURE! - in org.apache.arrow.flight.example.TestExampleServer
[ERROR] putStream(org.apache.arrow.flight.example.TestExampleServer)  Time elapsed: 0.129 s  <<< ERROR!
java.lang.IllegalStateException: 
Memory was leaked by query. Memory leaked: (66)
Allocator(flight-server) 0/66/134/9223372036854775807 (res/actual/peak/limit)
	at org.apache.arrow.flight.example.TestExampleServer.after(TestExampleServer.java:66)

This seems to fail both in JDK8 and JDK9 but not consistently

Reporter: Wes McKinney / @wesm
Assignee: Jacques Nadeau / @jacques-n

PRs and other links:

• GitHub Pull Request #2753

_{Note: This issue was originally created as ARROW-3343. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Seems like there may be a race condition that may trigger when the Travis VM is slower than normal

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 2753
#2753