[bp] got rid of unused ns_vbm_sup:kill_dst_children
[bp] got rid of unused ns_vbm_sup:kill_dst_children

Originally reviewed on http://review.couchbase.org/12345

Change-Id: Ie4869f2d3eaaf9e93ab76b55c5bf6549ffc53149
Reviewed-on: http://review.couchbase.org/13951
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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