Change nsenter options to unbreak WSL

Running the original script broke WSL. This change fixed it, thought I'm
not sure why. The options "-m -p" seem to conflict but what do I know.

Found at DamionGans#85.

enter-systemd-namespace

@@ -38,11 +38,11 @@ fi
 USER_HOME="$(getent passwd | awk -F: '$1=="'"$SUDO_USER"'" {print $6}')"
 if [ -n "$SYSTEMD_PID" ] && [ "$SYSTEMD_PID" != "1" ]; then
     if [ -n "$1" ] && [ "$1" != "bash --login" ] && [ "$1" != "/bin/bash --login" ]; then
-        exec /usr/bin/nsenter -t "$SYSTEMD_PID" -a \
+        exec /usr/bin/nsenter -t "$SYSTEMD_PID" -m -p \
             /usr/bin/sudo -H -u "$SUDO_USER" \
             /bin/bash -c 'set -a; [ -f "$HOME/.systemd-env" ] && source "$HOME/.systemd-env"; set +a; exec bash -c '"$(printf "%q" "$@")"
     else
-        exec /usr/bin/nsenter -t "$SYSTEMD_PID" -a \
+        exec /usr/bin/nsenter -t "$SYSTEMD_PID" -m -p \
             /bin/login -p -f "$SUDO_USER" \
             $([ -f "$USER_HOME/.systemd-env" ] && /bin/cat "$USER_HOME/.systemd-env" | xargs printf ' %q')
     fi