Mark internal backend as using "redisLockManager"

* This is a no-op since only the proxy backend matters and
  it already uses this. Nevertheless, this removes some
  misleading comments and makes this more future proof.

Change-Id: I40d99fbca4e2f11f26e211b1845b5737c6af67c6
Merge "Mark internal backend as using "redisLockManager""