Cirrus: Confirm networking is working

Thanks to @edsantiago for suggestion to use nc

Signed-off-by: Chris Evich <cevich@redhat.com>

.cirrus.yml

@@ -123,6 +123,9 @@ gating_task:
 
     timeout_in: 20m
 
+    networking_script:  # Don't bother going further if something is down
+        - 'while read host port; do nc -zv -w 13 $host $port || exit 1; done < ${CIRRUS_WORKING_DIR}/${SCRIPT_BASE}/required_host_ports.txt'
+
     gate_script:
         # N/B: entrypoint.sh resets $GOSRC (same as make clean)
         - '/usr/local/bin/entrypoint.sh install.tools |& ${TIMESTAMP}'

contrib/cirrus/required_host_ports.txt

@@ -0,0 +1,4 @@
+github.com 22
+docker.io 443
+quay.io 443
+registry.fedoraproject.org 443