Fix Redis After Configuration Group Merge

the configuration-group implementation forgot to update the
prepare() method for redis to include overrides. in addition, an
override.config.template is now required to avoid a fatal error in
the taskmanager.

Change-Id: If12a4e4c9f1bbb8e96a3ed443756f70398525bde
Closes-Bug: #1277390
Merge "Fix Redis After Configuration Group Merge"