Add timeout to XMPP IQ requests

[ralphm]

XMPP <iq/> stanzas are designed to have request-response behaviour. The current implementation of t.w.p.j.xmlstream.IQ has a send() method that returns a deferred which fires when a response has been received.

However, if for some reason the other party is too slow or unable to respond, it is desirable to have those deferreds fire with a failure that indicates no response has been received within a configured time period.

Note that the current implementation already fires the deferreds of all pending requests when the XML stream connection has been lost.

[ralphm]

Implemented in source:branches/xmpp-iq-timeout-2218.

To test timeouts, I used t.i.task.Clock, and uncovered that it doesn't set its called attribute properly, as mentioned in #2222. This branch contains a fix for this.

Please review.

[exarkun]

Fix to task.py looks good. Timeout support added to jabber mostly looks good. I wonder what will happen if a response is received after the timeout expires, though. Add a test for this case?

[ralphm]

Nothing happens, since the iq's id is removed from the iqDeferreds dictionary. The existing tests already test this. I did add a test for making sure untracked iq responses (id not in that dictionary) are passed untouched to the next observer.

[exarkun]

Looks good. Go ahead and merge.

[ralphm]

(In [18644]) Add timeout behaviour to xmpp iq requests and make t.i.Clock set call.called.

Author: ralphm Reviewer: exarkun Fixes #2218 and #2222