Log translation hint for Heat.tests
Log translation hint for Heat.tests

Currently, Log translation is motivated by oslo's move to prioritized
translation of strings, as documented at
https://wiki.openstack.org/wiki/LoggingStandards#Log_Translation

- add log translation hints for warning, error and info levels
- move from LOG.warning to LOG.warn
- remove use of % as a string formatter, use the log functionality
  instead

Partial implements blueprint log-translation-hints

Change-Id: Ia961196df09d301b4c384ffe51413ffc5c15164e

openstack/heat,dragorosson/heat,gonzolino/heat,srznew/heat,maestro-hybrid-cloud/heat,redhat-openstack/heat,srznew/heat,takeshineshiro/heat,miguelgrinberg/heat,cwolferh/heat-scratch,pratikmallya/heat,steveb/heat,noironetworks/heat,jasondunsmore/heat,dims/heat,rdo-management/heat,dims/heat,maestro-hybrid-cloud/heat,dragorosson/heat,pshchelo/heat,pratikmallya/heat,steveb/heat,cwolferh/heat-scratch,cryptickp/heat,noironetworks/heat,openstack/heat,rh-s/heat,takeshineshiro/heat,rh-s/heat,gonzolino/heat,redhat-openstack/heat,rdo-management/heat,miguelgrinberg/heat,pshchelo/heat,cryptickp/heat,jasondunsmore/heat