MTR save - compress all at once, and save plugins if there are cores

By doing exec false, find will return non-0 on there being matches
and then tar can save the plugins, de-referencing the list of
symlinks make by mtr.

Author: grooverdan

configuration/steps/commands/mtr.py

@@ -73,7 +73,7 @@ def _save_logs(self) -> str:
             echo "Saving MTR logs to persistent volume because some tests failed"
             cd {self.log_path}
             mkdir -p {self.save_logs_path}
-            time find . -iregex ".*/core\(\.[0-9]+\)" -ls  -exec gzip {} \;
+            time find . -iregex ".*/core\(\.[0-9]+\)" -ls  -exec gzip \{\} + -exec false \{\} + || tar -czvf {self.save_logs_path}/plugins.tar.gz --dereference mysql-test/var/plugins
             find . -type f \( {patterns} \) -print0 | rsync -a --files-from=- --from0 ./ {self.save_logs_path}/
             exit 1
             """