LockManagerGroupFactory to replace singletons

LockManagerGroupFactory to replace singletons

100% test coverage of code that appears to be working and used, in both
LockManagerGroupFactory and also LockManagerGroup. Where possible I
wrote it as unit tests. One preexisting code path seems to be broken and
I marked the test as skipped. Two methods look unused and perhaps not
especially helpful, so I didn't write tests for them yet in case we want
to just get rid of them instead.

Change-Id: Iaa7354f31c451b87773468609c674a3bf1d4382f