hippotatd: add a startup message

[hippotat] / fake-userv

#!/bin/sh
set -ex
echo >&2 "$0: invoked as $0 $*"
exec 3<&0 4>&1 5>&2 >&2 </dev/null
exec xterm -geometry -0+0 -T netns -e unshare -n -- sh -xc '
  "$@" <&3 >&4 2>&5 &
  sleep 0.1
  env - bash -i
' x "$@"