MB-10220 Add {tags, undefined} to past maps when appropriate.

Otherwise it prevents vbucket map generation code from using these
maps since map options are differrent.

Note that http://review.couchbase.org/#/c/34220/3 fixes this in a
better way. Here I just wanted the change to be minimal.

Change-Id: I5b94c1e43fb94e38422a68ffc97ec37bacc1cfb7
Reviewed-on: http://review.couchbase.org/34246
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Merge remote-tracking branch 'origin/for-rackaware' into master

* origin/for-rackaware:
  MB-10220 Add {tags, undefined} to past maps when appropriate.

This merge is empty because MB-10220 is fixed differently on master

Change-Id: I44b0ed719c361f04d137192711729fb0d14e6233