Some errors printed the jail name for unnamed (command line) jails.
Attempting to create an already-existing jail from the command line
returned with no error (even for non-root) due to bad logic in
start_state.
Ignore kvm_proc errors, which are typically caused by permission
problems. Instead, stop ignoring permission errors when removing
a jail (but continue to silently ignore other errors, i.e. the
jail no longer existing). This makes non-root attempts at removing
a jail give a clearer error message.