Catch errors

[KwikKill]

Currently, when some unplanned response is raised from the ipset command, it crashed netcontrol. This is making apps that rely on it waiting for a timeout instead of aborting.

For example, when querying "get_user_info" with an unknown MAC, the message is "Did not find info about MAC 00:00:00:00:00:00" which is then going through "to_dict()" python method and cause a crash.

This sort of error should be handled even if it should not happen.