Clear file_lists caches on master start

The caches do expire quickly (30 sec by default), but if you make a
config change, then quickly restart the master, the caches will still be
younger than the expiry deadline. This commit clears all file lists
caches on master start to ensure that they are properly generated in the
first loop interval.

salt/daemons/masterapi.py

@@ -5,9 +5,10 @@ involves preparing the three listeners and the workers needed by the master.
 '''
 
 # Import python libs
+import fnmatch
+import logging
 import os
 import re
-import logging
 import time
 try:
     import pwd
@@ -76,7 +77,7 @@ def clean_fsbackend(opts):
     '''
     Clean out the old fileserver backends
     '''
-    # Clear remote fileserver backend env cache so it gets recreated
+    # Clear remote fileserver backend caches so they get recreated
     for backend in ('git', 'hg', 'svn'):
         if backend in opts['fileserver_backend']:
             env_cache = os.path.join(
@@ -94,6 +95,25 @@ def clean_fsbackend(opts):
                         .format(env_cache, exc)
                     )
 
+            file_lists_dir = os.path.join(
+                opts['cachedir'],
+                'file_lists',
+                '{0}fs'.format(backend)
+            )
+            try:
+                file_lists_caches = os.listdir(file_lists_dir)
+            except OSError:
+                continue
+            for file_lists_cache in fnmatch.filter(file_lists_caches, '*.p'):
+                cache_file = os.path.join(file_lists_dir, file_lists_cache)
+                try:
+                    os.remove(cache_file)
+                except (IOError, OSError) as exc:
+                    log.critical(
+                        'Unable to file_lists cache file {0}: {1}'
+                        .format(cache_file, exc)
+                    )
+
 
 def clean_expired_tokens(opts):
     '''
@@ -704,7 +724,7 @@ class RemoteFuncs(object):
                 if 'jid' in minion:
                     ret['__jid__'] = minion['jid']
         for key, val in self.local.get_cache_returns(ret['__jid__']).items():
-            if not key in ret:
+            if key not in ret:
                 ret[key] = val
         if load.get('form', '') != 'full':
             ret.pop('__jid__')