Replacing variable logger on LOG

Commit https://review.openstack.org/#/c/94255/1 introduces check for
translating log messages. This check uses in pattern name 'LOG', so in
heat code also should be used this name intead of 'logger'. Also same
name is used in other projects.

Change-Id: Iba24c7eb1c13e68a91d090d7bcdbcb40d6e16071
Partial-Bug: #1321283
Merge "Replacing variable logger on LOG"