Fixed the "target modules list" to not crash in Debug builds due to an...

Fixed the "target modules list" to not crash in Debug builds due to an assertion where the mutex in the "module_list" local variable would assert when the lldb_private::Mutex would destruct. What was happening was the mutex in the module list was being locked by a local locker object and then "module_list" would get destroyed before the locker and the locker still had the mutex locked which would cause the pthread call to destroy the mutex to fail with "Resource busy" and it would cause a mutex leak.

llvm-svn: 159291