Ensure /var/log/heat/engine.log is owned by heat

If heat-manage db_sync creates the logfile before the
heat engine service then it will be owned by root causing
heat-engine to error.

Fixes bug 1199789

Change-Id: Ib23a0d46ebf354a3293a64215715038497faf5b0
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Change-Id: Id57e176ec2daa6a0025a9c8ac73f6ef6e654284d