[9] RFR: 8164159: java/nio/file/WatchService/UpdateInterference.java test leaves daemon threads

[Artem Smotrakov]

Hello,

Please review the following patch for 
java/nio/file/WatchService/UpdateInterference.java test.

The test creates a couple of daemon threads which have an infinite loop 
inside. When the test finishes, those daemon still keep running as long 
as jtreg use this instance of JVM to run other tests (the test doesn't 
run in othervm mode).

The test also creates a WatchService which creates a 
"FileSystemWatchService" daemon thread. Then, the test doesn't close 
this WatchService, and as a result, this daemon thread keeps running as 
well.

The test shouldn't leave daemon threads when it finishes. It may slow 
down further test execution. If other tests also leave daemon threads, 
it may cause intermittent test failures, see for example JDK-8160642 and 
JDK-8162757.

The patch updates the test with the following:
- threads are not daemons any more
- "while" loops are not infinite
- the test waits for threads to finish before closing a watch service to 
avoid ClosedWatchServiceException
- the test closes a watch service in try-with-resources block
- the test removes temporary files and directories in the end

Bug: https://bugs.openjdk.java.net/browse/JDK-8164159
Webrev: http://cr.openjdk.java.net/~asmotrak/8164159/webrev.00/

Artem