monitor: use net.UnixListener for unix sockets
monitor: use net.UnixListener for unix sockets

Also ensure that the socket is closed and file removed on failure.

Signed-off-by: Alexandre Perrin <60c6d277a8bd81de7fdde19201bf9c58a3df08f4@kaworu.ch>

tgraf/cilium,tklauser/cilium,cilium/cilium,michi-covalent/cilium,cilium-team/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,michi-covalent/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,tklauser/cilium,cilium-team/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium