Don't crash if a memcached bucket is already there.
Don't crash if a memcached bucket is already there.

Change-Id: If13d8c6c6e42cc37acebc3fb21b0b7a4e4b0bb4f
Reviewed-on: http://review.northscale.com/3200
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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