testing_using_container: fix port forwarding

--network=host tries to use privileged ports on the host
so it fails when run as user. Go back to port forwarding.

Also, let podman pick a number and print it.

doc/testing_using_container.md

@@ -11,7 +11,6 @@ script. That scripts does several steps:
   (using the [setup.sh](../setup.sh) script)
 - It asks for the new root password to allow logging in (by default there is
   no root password set in containers)
-- It provides web UI on default host HTTP/HTTPS ports (connect to
-  `http://localhost`, port forwarding does not work for some reason)
+- It provides web UI on a forwarded HTTPS port
 - Starts a shell inside the container with root access for more testing or
   debugging.

testing_using_container.sh

@@ -6,7 +6,7 @@
 #
 # Details:
 # - container name: agama
-# - port 9091 is exposed and forwarded to the container
+# - SSL port is exposed (to a random port, printed out) so that web UI works
 # - 'WITH_RUBY_DBUS=1 $0' will prefer ../ruby-dbus to any ruby-dbus.gem
 
 set -x
@@ -34,12 +34,11 @@ if [ "${WITH_RUBY_DBUS-}" = 1 ]; then
   MORE_VOLUMES=(-v ../ruby-dbus:/checkout-ruby-dbus)
 fi
 
-# use the host networking, port forwarding does not work for some reason :-/
 podman run --name ${CNAME?} \
   --privileged --detach \
   -v .:/checkout \
   ${MORE_VOLUMES[@]} \
-  --network=host \
+  -p :443 \
   ${CIMAGE?}
 
 # shortcut for the following
@@ -50,11 +49,18 @@ ${CEXEC?} "cd /checkout && ./setup.sh"
 echo "Set the Agama (root) password:"
 podman exec -it ${CNAME?} passwd
 
-# Interactive shell in the container
-podman exec --tty --interactive ${CNAME?} bash
+PORT=$(podman port ${CNAME?} 443)
+PORT=${PORT#*:}
 
+set +x
+echo "agama-web-server (container port 443) forwarded to https://localhost:$PORT/"
 echo "To attach again to the Agama container run:"
 echo "    podman exec --tty --interactive ${CNAME?} bash"
 echo "To stop and remove the Agama container run:"
 echo "    podman stop ${CNAME?}"
 echo "    podman rm ${CNAME?}"
+set -x
+
+# Interactive shell in the container
+podman exec --tty --interactive ${CNAME?} bash
+