Review Request: JDK-8190911: tools/jdeps/MultiReleaseJar.java failed with java.lang.IllegalThreadStateException

[mandy chung]

This is a simple test fix. The test fails because it calls 
Process.exitValue() but the process hasn't exited.  The test should wait 
for the process to terminate or let it to timeout if something goes wrong.

Webrev:
http://cr.openjdk.java.net/~mchung/jdk10/webrevs/8190911/webrev.00/
Mandy