handle undefined vbucket maps during failover. CBSE-40
handle undefined vbucket maps during failover. CBSE-40

Particularly, it was possible to create bucket when one of nodes is
down. That prevents janitor from assigning vbucket map. And this
causes fail over code to see undefined vbucket map, which is handled
now by doing nothing with such vbucket maps.

Change-Id: Iee8c33abec6bd11513b4f9e4d0a48042f719ed84
Reviewed-on: http://review.couchbase.org/11615
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

membase/ns_server,ceejatec/ns_server,daverigby/ns_server,t3rm1n4l/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,membase/ns_server,daverigby/ns_server,vzasade/ns_server,membase/ns_server,membase/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,vzasade/ns_server,pavel-blagodov/ns_server,mschoch/ns_server,ceejatec/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,nimishzynga/ns_server,ceejatec/ns_server,daverigby/ns_server,daverigby/ns_server,vzasade/ns_server,nimishzynga/ns_server,mschoch/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,pavel-blagodov/ns_server,t3rm1n4l/ns_server,pavel-blagodov/ns_server,ceejatec/ns_server,daverigby/ns_server,ceejatec/ns_server,membase/ns_server,pavel-blagodov/ns_server,ceejatec/ns_server,membase/ns_server,vzasade/ns_server