made ns_heart send initial heartbeat immediately
made ns_heart send initial heartbeat immediately

So that other nodes have up-to-date information on this node without
heartbeat period delay.

Change-Id: If449e0e9c94e12c849e164fcdccda0776999811a
Reviewed-on: http://review.couchbase.org/11237
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

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