[PATCH][bodhi] Fix a bug in our masher sanity check

[Luke Macken]

There is a bug in bodhi's new pre-push sanity checker that causes the
mashing lockfile to get wiped out when a push is resumed and the sanity
check fails.

I would like to push this patch out to releng2 and relepel01 only.

--- a/bodhi/masher.py
+++ b/bodhi/masher.py
@@ -641,7 +641,6 @@ class MashTask(Thread):
             if self.resume:
                 if not self.safe_to_resume():
                     log.error("safe_to_resume failed! -- aborting")
-                    self._unlock()
                     masher.done(self)
                     return
             else: