gitlab CI: retry the VM jobs on script failure

Unfortunately the various VM jobs are timing sensitive and create a bunch of
false positives if the runners are under load and miss out on some of the
events (the tablet proximity handling is a particularly bad test here).
Let's retry on failure first to give the CI more opportunity to maybe succeed.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

.gitlab-ci.yml

@@ -531,6 +531,9 @@ freebsd:11.2@container-clean:
       junit: $MESON_BUILDDIR/junit-*.xml
 
   allow_failure: true
+  retry:
+    max: 2
+    when: script_failure
   needs: ['fedora:30@qemu-prep']
 
 # in reverse order of duration to get the slowest ones started first