RFR: 6983747: Clean up of unused dl_mutex lock.

[Max Ockner]

Hello,
please review my clean up of the unused dl_mutex lock.

Bug: https://bugs.openjdk.java.net/browse/JDK-6983747
Webrev: http://cr.openjdk.java.net/~mockner/6983747/
Summary: Deleted all references to the dl_mutex lock which was no longer 
used.

Tested with jtreg runtime tests.


Thanks,
Max Ockner