Cross-platform changes to onos.initd

We now can use start-stop-daemon (debian), daemon()
shell function (centos), or sudo (others) to start
onos-service.

It should be backward compatible on systemd systems.

Tested on Ubuntu 14 and CentOS 6. Should also work on
Ubuntu 15/16, CentOS 7, Debian, and Fedora.

(Note that we should test this against various OSes,
preferably automatically rather than manually!)

Addresses at least part of ONOS-2907

Change-Id: I4ded98baf02321a5a9db37fdff19e1ce4a3d23d2
diff --git a/tools/test/bin/onos-service b/tools/test/bin/onos-service
index 43c231c..eab52ed 100755
--- a/tools/test/bin/onos-service
+++ b/tools/test/bin/onos-service
@@ -43,7 +43,7 @@
 
         # Execute the remote commands
         for node in $nodes; do
-            ssh $ONOS_USER@${node} "sudo service onos ${2:-status}"
+            ssh -tt $ONOS_USER@${node} "sudo service onos ${2:-status}"
         done
     ;;
     *)