engine: Use AutoCloseableLock in MacPoolManagerRanges

Refactored MacPoolManagerRanges to use the AutoCloseableLock to simplify
lock blocks.

Change-Id: I5fdb1cb8c302e88dbcbdc434313a6b11f7b15d5b
Signed-off-by: Mike Kolesnik <mkolesni@redhat.com>