Make ns_memcached:backfilling backwards compatible
Make ns_memcached:backfilling backwards compatible

Can't do a cross-node call because I didn't put in a catch-all.

Change-Id: I5138e052b5c6cd250329a1afb54628c4963fd995
Reviewed-on: http://review.membase.org/3545
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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