Intermittent test failure - PresenceSuite.TestWatchPeriod

[Tim Penhey]

Hi guys,

I have filed a bug for this intermittent failure:
  https://bugs.launchpad.net/juju-core/+bug/1187612

I have no idea why it is failing, but looks to be very timing based.  My
guess is there is a synchronization point missing as the test starts a
go routine that does something, and continues with the checks.  Seems to
be no attempt to wait on any synchronization point (at least that I
could see) before the asserts.

Tim