Handle multi-process SIGHUP correctly

Child processes were returning to the main while loop
and spawning a next generation of processes. Instead
they should exit cleanly.

Fix for bug 1042823.

Change-Id: I8c0d150640c78487b43279a44d0d6d3ac3e386cc

glance/common/wsgi.py

@@ -251,7 +251,9 @@ def run_child(self):
             signal.signal(signal.SIGINT, signal.SIG_IGN)
             self.run_server()
             self.logger.info(_('Child %d exiting normally') % os.getpid())
-            return
+            # self.pool.waitall() has been called by run_server, so
+            # its safe to exit here
+            sys.exit(0)
         else:
             self.logger.info(_('Started child %s') % pid)
             self.children.append(pid)