Modify nova.wsgi.start() should check backlog parameter.

Fixes bug 883292.

Forward ported from
https://github.com/ntt-pf-lab/nova/tree/openstack-qa-nova-883292

Change-Id: I8839851a72fcf0910a532d558ffe66a39a7db1e8

Authors

@@ -167,6 +167,7 @@ Salvatore Orlando <salvatore.orlando@eu.citrix.com>
 Sandy Walsh <sandy.walsh@rackspace.com>
 Sateesh Chodapuneedi <sateesh.chodapuneedi@citrix.com>
 Scott Moser <smoser@ubuntu.com>
+Sean Dague <sdague@linux.vnet.ibm.com>
 Soren Hansen <soren.hansen@rackspace.com>
 Stanislaw Pitucha <stanislaw.pitucha@hp.com>
 Stephanie Reese <reese.sm@gmail.com>

nova/wsgi.py

@@ -85,8 +85,12 @@ def start(self, backlog=128):
 
         :param backlog: Maximum number of queued connections.
         :returns: None
+        :raises: nova.exception.InvalidInput
 
         """
+        if backlog < 1:
+            raise exception.InvalidInput(
+                    reason='The backlog must be more than 1')
         self._socket = eventlet.listen((self.host, self.port), backlog=backlog)
         self._server = eventlet.spawn(self._start)
         (self.host, self.port) = self._socket.getsockname()