Revert r64441
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64448 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Revert r64441
"thread_sync.c (rb_mutex_synchronize): only unlock if we own the mutex"
Mutex#synchronize, even if an exception interrupts ConditionVariable#wait.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64448 b2dd03c8-39d4-4d8f-98ff-823fe69b080e