Fix for 6984287: Regularize how GC parallel workers are specified, caused CMS to hang:

----------------- lwp# 3 / thread# 3 --------------------
 fffffd7ffedfd262 ???????? () + ffffffffffb36252
 fffffd7ffe9fa619 __1cTCMSRefProcTaskProxyNdo_work_steal6MipnbECMSParDrainMarkingStackClosure_pnWCMSParKeepAliveClosure_pi_v_ () + 7b9
 fffffd7ffe9f9d83 __1cTCMSRefProcTaskProxyEwork6Mi_v_ () + 293
 fffffd7ffeed2238 __1cKGangWorkerEloop6M_v_ () + d8
 fffffd7ffeed2129 __1cKGangWorkerDrun6M_v_ () + 29
 fffffd7ffed7b849 java_start () + 1f9
 fffffd7fff2c6ddb _thr_setup () + 5b
 fffffd7fff2c7010 _lwp_start ()
----------------- lwp# 4 / thread# 4 --------------------
 fffffd7ffee52ed7 __1cWParallelTaskTerminatorRoffer_termination6MpnUTerminatorTerminator__b_ () + c7
 fffffd7ffe9fa619 __1cTCMSRefProcTaskProxyNdo_work_steal6MipnbECMSParDrainMarkingStackClosure_pnWCMSParKeepAliveClosure_pi_v_ () + 7b9
 fffffd7ffe9f9d83 __1cTCMSRefProcTaskProxyEwork6Mi_v_ () + 293
 fffffd7ffeed2238 __1cKGangWorkerEloop6M_v_ () + d8
 fffffd7ffeed2129 __1cKGangWorkerDrun6M_v_ () + 29
 fffffd7ffed7b849 java_start () + 1f9
 fffffd7fff2c6ddb _thr_setup () + 5b
 fffffd7fff2c7010 _lwp_start ()

This issue is fixed in 7 with 6668573: CMS: reference processing crash if ParallelCMSThreads > ParallelGCThreads.

This needs to be fixed in jdk 6 as well.