Allow running simple_switch with custom arguments about p4app HOT 2 OPEN

I'm not too familiar with this repo, but you will probably need to do the following:

• update this Python file so that the extra argument is provided to the bmv2 process: https://github.com/p4lang/p4app/blob/master/docker/scripts/mininet/p4_mininet.py
• rebuild the p4app docker image locally, probably with a command like this one: docker built -t p4app:latest .
• run p4app again (which should use your new local image, unless you run p4app update)

Note that the filename you provide with --notification-addr will be located inside the docker container IIRC, so if you want to access it from the machine which is running the container, you will need to update the volume mounts for the container accordingly (https://github.com/p4lang/p4app/blob/master/p4app#L55).

Depending on what you are trying to do, it may be better not to use p4app and run the different components yourself (bmv2, p4c).

from p4app.

I modified the p4_mininet.py file but it doesn't make any effect. I think that when the docker image is built there is installed internally another p4app files, so it doesn't take the changes into account... The folder container_name:/scripts in the current container should be updated with the new scripts (for example the p4_mininet.py script or others). I would like to modify the IP host address, the interface name and the Mac address but I couldn't do it.

from p4app.