Ensure glance-api application is "greened"

Fixes bug 1052640

Avoid unresponsiveness during long-lived I/O-bound operations by
ensuring that the standard socket libraries are monkey-patched in
all code-paths.

Change-Id: If672c26f2b462d1abcfc86e20256957f73f98fde

glance/common/wsgi.py

@@ -193,7 +193,7 @@ def hup(*args):
 
         if CONF.workers == 0:
             # Useful for profiling, test, debug etc.
-            self.pool = eventlet.GreenPool(size=self.threads)
+            self.pool = self.create_pool()
             self.pool.spawn_n(self._single_run, self.app_func(), self.sock)
             return
         else:
@@ -204,6 +204,10 @@ def hup(*args):
             while len(self.children) < CONF.workers:
                 self.run_child()
 
+    def create_pool(self):
+        eventlet.patcher.monkey_patch(all=False, socket=True)
+        return eventlet.GreenPool(size=self.threads)
+
     def wait_on_children(self):
         while self.running:
             try:
@@ -266,8 +270,7 @@ def run_server(self):
         except Exception:
             msg = _("eventlet 'poll' hub is not available on this platform")
             raise exception.WorkerCreationFailure(reason=msg)
-        eventlet.patcher.monkey_patch(all=False, socket=True)
-        self.pool = eventlet.GreenPool(size=self.threads)
+        self.pool = self.create_pool()
         try:
             eventlet.wsgi.server(self.sock, self.app_func(),
                     log=WritableLogger(self.logger), custom_pool=self.pool)