Update mozsvc for latest tokenserver/hawkauth changes

This switches to using hawkauth instead of the older macauth, and removed references to "Sagrada" in favour of the more generic "TokenServer".  Necessary if we want to build sync1.5 from the old sync2.0 codebase.

The only serious change here is to nonce-handling, which is substantially simplified in hawk.  We no longer need to calculate and store a clock-skew for each user, just remember previously-seen (timestamp, nonce) pairs.

@telliott r?