Instead of waiting for const seconds, need to have a proc to wait for daemon port to be open

[Vedamurthy Joshi]

In the tests, we usually wait for 30 sec, 60 sec etc. after restarting a process.

Instead, we should have a method to wait for the process' port number (in LISTEN state) with retries in place.
For ex : 9100 for contrail-api, 8083 for control-node etc...

It should be something like wait_for_port(server, port) with retry decorator.

Also, this needs to be go into all the places where we are currently doing inputs.restart_server() calls