Prefer adding vbucket to passive index over replica one.
Prefer adding vbucket to passive index over replica one.

Thus when some vbucket is moved to some of replica nodes, it
will be added to a main index as soon as possible. This prevents
rebalance from getting stuck.

Change-Id: I6798541e9fbd0d5c3f5f3f87768138345bb9437e
Reviewed-on: http://review.couchbase.org/12363
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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