vbucket_map_to_json() helper func
vbucket_map_to_json() helper func

Change-Id: Ic880576e00b3c7c2238b5460557ecca0b1ef6e82
Reviewed-on: http://review.northscale.com:8080/312
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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