RFR 8052961: Test "com/sun/tools/attach/StartManagementAgent.java" failing intermittently

[Jaroslav Bachorik]

Please, review this (hopefully last) change to StartManagementAgent test
Issue : https://bugs.openjdk.java.net/browse/JDK-8052961
Webrev: http://cr.openjdk.java.net/~jbachorik/8052961/webrev.00

The test needs a properly registered service for the ServiceLoader - but 
it fails to compile the provider class explicitly leading to 
intermittent failures. The fix is to add the "SimpleProvider" to "@run 
build ..." line.

Thanks,

-JB-