RFR: 6804470 JvmstatCountersTest.java test times out on slower machines

[Jaroslav Bachorik]

Please, review the following simple change.

The test times out on slower machines and I was able to reproduce the 
failure even on a normally fast machine using the fastdebug build. The 
timeout does not occur on every run - more like once in 10-15 runs.

There is nothing really wrong with the test - it just takes rather long 
time to obtain the jvmstat counters. The remedy is to specify a longer 
timeout and see if it is enough. I am using 10 minutes for the timeout 
in the patch.

Issue : https://bugs.openjdk.java.net/browse/JDK-6804470
Webrev: http://cr.openjdk.java.net/~jbachorik/6804470/webrev.00

Thanks,

-JB-