Fix Redis increment behavior by using BagOStuff->incr instead

Due to the PHP serialization, the Redis native INCR and INCRBY do not
work.  This instead falls back on the parent class's incr, which uses
lock and unlock, and incrementing on the PHP side.

Bug: 55986
Change-Id: I500199aeb935963ca118fde163bd7ba0cba8f79f
Merge "Fix Redis increment behavior by using BagOStuff->incr instead"