Fixed explicit mutex unlock straggler.
Fixed explicit mutex unlock straggler.

This got left in when I was trying to get the mutex to properly unlock across
fork() calls in both parent and child process.

jsyeo/rubinius,jsyeo/rubinius,kachick/rubinius,jsyeo/rubinius,kachick/rubinius,jsyeo/rubinius,kachick/rubinius,kachick/rubinius,kachick/rubinius,jsyeo/rubinius,jsyeo/rubinius,kachick/rubinius,jsyeo/rubinius,kachick/rubinius,kachick/rubinius