fixed validation message for remote clusters REST API
fixed validation message for remote clusters REST API

Change-Id: I85e9629dac9de8d185fa775f7a0b9f8a7cb14c86
Reviewed-on: http://review.couchbase.org/9974
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Benjamin Young <fe09bc2ef2737a3258f978e26226dcbac1b3f948@couchbase.com>

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