Fixed keeping a lock unneededly while scanning is complete

This change little effect on the application itself, as the
lock.aquire() was never touched again when the detection already took
place. Since Django initializes the application first, this locking
wasn't really needed anymore for web-based applications.

Author: vdboor

fluent_contents/extensions/pluginpool.py

@@ -232,13 +232,13 @@ def _import_plugins(self):
         if self.detected:
             return
 
-        # In some cases, plugin scanning may start during a request.
-        # Make sure there is only one thread scanning for plugins.
-        self.scanLock.acquire()
-        if self.detected:
-            return  # previous threaded released + completed
-
         try:
+            # In some cases, plugin scanning may start during a request.
+            # Make sure there is only one thread scanning for plugins.
+            self.scanLock.acquire()
+            if self.detected:
+                return  # previous threaded released + completed
+
             import_apps_submodule("content_plugins")
             self.detected = True
         finally: