Allow to search for trivially matching past vbucket maps.
Allow to search for trivially matching past vbucket maps.

Where by "trivial" I mean:

  - nodes sets of past map and current map are the same
  - tags might be renamed but if two nodes were on the same tag before
  renaming they must reside on the same tag after the renaming.

Change-Id: If8178faa868397c3241092266ab78e0e3a5b460a
Reviewed-on: http://review.couchbase.org/38281
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

membase/ns_server,nimishzynga/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,membase/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,membase/ns_server,ceejatec/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,mschoch/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,membase/ns_server,membase/ns_server,mschoch/ns_server