Remove Cyrus SASL from XMPP

This will eventually be replaced by Hasl, but XMPP has it's own built-in SASL
mechanisms as well as Cyrus, so removing Cyrus first is just the first step.

Testing Done:
Connected an XMPP account, sent direct messages from both sides, and joined a muc and sent messages from both sides as well.
Also ran the unit tests.

Reviewed at https://reviews.imfreedom.org/r/2295/