toolkit/mozapps/extensions/test/xpcshell/test_update.js and toolkit/mozapps/extensions/test/xpcshell-unpack/test_update.js test hangs

This has been failing for a while now. Unfortunately, not sure when it started failing because jenkins doesn't retain enough history.

The hang occurs when shutting down the http server, because there are connections that remain open. It looks like it's these 4 connections which are never closed, but I've got no idea where they are coming from:

HTTPD-INFO | *** onSocketAccepted(socket=[xpconnect wrapped nsIServerSocket], trans=[xpconnect wrapped (nsISupports, nsISocketTransport, nsITransport, nsIDNSListener)])
HTTPD-INFO | >>> new connection on 127.0.0.1:52550
HTTPD-INFO | *** opening new connection 36 on port 52550
HTTPD-INFO | *** starting connection 36
HTTPD-INFO | *** onSocketAccepted(socket=[xpconnect wrapped nsIServerSocket], trans=[xpconnect wrapped (nsISupports, nsISocketTransport, nsITransport, nsIDNSListener)])
HTTPD-INFO | >>> new connection on 127.0.0.1:52551
HTTPD-INFO | *** opening new connection 37 on port 52551
HTTPD-INFO | *** starting connection 37
HTTPD-INFO | *** onSocketAccepted(socket=[xpconnect wrapped nsIServerSocket], trans=[xpconnect wrapped (nsISupports, nsISocketTransport, nsITransport, nsIDNSListener)])
HTTPD-INFO | >>> new connection on 127.0.0.1:52552
HTTPD-INFO | *** opening new connection 38 on port 52552
HTTPD-INFO | *** starting connection 38
HTTPD-INFO | *** onSocketAccepted(socket=[xpconnect wrapped nsIServerSocket], trans=[xpconnect wrapped (nsISupports, nsISocketTransport, nsITransport, nsIDNSListener)])
HTTPD-INFO | >>> new connection on 127.0.0.1:52553
HTTPD-INFO | *** opening new connection 39 on port 52553
HTTPD-INFO | *** starting connection 39