open5gs: Add pgw.sh

This can serve as an entrypoint for running open5gs-pgw inside
the open5gs-master container.  It will run setup.sh to create the ogstun
device, followed by running open5gs-pgwd as 'osmocom' user.

Change-Id: I4527b5e328fb248552e69961b80b9f791ec74293

open5gs-master/Dockerfile

@@ -44,6 +44,7 @@ RUN apt-get update && \
     apt-get clean
 
 COPY setup.sh /root
+COPY pgw.sh /root
 
 # crate user
 ARG username=osmocom

open5gs-master/pgw.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+set -e
+set -x
+/root/setup.sh
+su - osmocom -c "open5gs-pgwd $*"