heat common : quieten policy logging

Policy logs the currently loaded policy for every request, which is
too noisy even for debug - we already log the file which contains
the policy when we load it, so this is probably sufficient.

fixes bug 1150091

Change-Id: I0891a30793375c7a0a6b2856db4377eecfeaad8e
Merge "heat common : quieten policy logging"