system tests: cleanup networks on teardown

When a test which creates a network fail it will not remove the network.
The teardown logic should remove the networks. Since there is no --all
option for network rm we use network prune --force.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

test/system/helpers.bash

@@ -108,6 +108,7 @@ function basic_teardown() {
     echo "# [teardown]" >&2
     run_podman '?' pod rm -t 0 --all --force --ignore
     run_podman '?'     rm -t 0 --all --force --ignore
+    run_podman '?' network prune --force
 
     command rm -rf $PODMAN_TMPDIR
 }