MB-11954: made wizard deal with with existing default bucket
MB-11954: made wizard deal with with existing default bucket

We now detect if default bucket already exists. And if so we update
it, rather than try to create it.

Change-Id: I8d7a39c2efaaae83ad78f24288b0a52915270b7c
Reviewed-on: http://review.couchbase.org/40598
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

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