Fix regression in wakeConnections

In d5e03ac9307c9cc6f79fc22f15e177d3662dc936, an optional argument
to wakeConnections was added so that only connections related to
a job would be awoken.  However, the default value, None, meant
that no connection would be awoken.  This doesn't make much sense,
and indeed, Zuul, in its unit tests, was relying on all connections
being awoken.  Fix this by awakening all connections if the job
argument is None (which never happens within gear itself).

Change-Id: Ib7632ae0353c414cc1b68dbe430cb57292058012

• gear/__init__.py[diff]