Fix race condition in project directory creation (#358)

Author: cigamit

awx/main/tasks/jobs.py

@@ -377,8 +377,7 @@ def release_lock(self, project):
         self.lock_fd = None
 
     def acquire_lock(self, project, unified_job_id=None):
-        if not os.path.exists(settings.PROJECTS_ROOT):
-            os.mkdir(settings.PROJECTS_ROOT)
+        os.makedirs(settings.PROJECTS_ROOT, exist_ok=True)
 
         lock_path = project.get_lock_file()
         if lock_path is None: