patch 8.2.2158: CI on cirrus times out, coveralls doesn't always run

Problem:    CI on cirrus times out, coveralls doesn't always run.
Solution:   Set timeout to 20 minutes. Adjust condition. (closes #7493)
diff --git a/.cirrus.yml b/.cirrus.yml
index a098789..4d78085 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -3,6 +3,8 @@
   FEATURES: huge
 
 freebsd_12_task:
+  only_if: $CIRRUS_TAG == ''
+  timeout_in: 20m
   freebsd_instance:
     image: freebsd-12-1-release-amd64
   install_script: