Add dependancy on supervisor package for the contrail packages.
Packages impacted are:
1) contrail-analytics,
2) contrail-config,
3) contrail-control and
4) contrail-vrouter
Processes in these packages will be started by supervisor.
Please also note that we will be using official version of supervisor package.

We also got rid of pkill/kill_all hack in contrail-config upstart file where
we were killing any left over process. This was no longer needed as we already
made sure that there were no leftover child processes once a service shutdown.

Closes-PR: 1354579

Change-Id: If89b87b769f03128d2ef3ce811e2c615d84b6c66