make obfsvpns start method blocking so that we can either handle errors and abort a VPN connection attempt or wait until obfsvpn is in a running state before we start openvpn to connect to obfsvpn for transparent proxying the traffic
try to restart obfsvpn in on different proxy port in case the default one is already bound
More generally this MR reduces the amount of cases where obfsvpn gets into a unusable state after changing settings such as locations or obfuscation settings while the VPN is running. In those cases sometimes the VPN constantly failed to re-connect and only killing and restarting the app resolved the issue.
