Add default QPID_HOST

Change 056df827ff3f8d40eeeedea3d09daae86982e5b5 added QPID_HOST
without a default.  This leaves a blank config line which confuses the
heck out of just about every daemon

Change-Id: Ibc4b5e5349fd6347d0100431f9347f1eff4aaf83