Index zuul executor

It would be useful to know what zuul executor ran a job so that we can
track potential executor specific issues back to that executor via
logstash. Add the zuul executors hostname to the log processing payload
which will result in us storing it in elasticsearch.

Change-Id: Ifbd7c7f91a006bd63e3df6053297ccc36bb3240b

roles/submit-log-processor-jobs/library/submit_log_processor_jobs.py

@@ -166,6 +166,8 @@ class LogMatcher(object):
         fields["node_provider"] = node['nodepool']['provider']
         log_url = urllib.parse.urljoin(self.log_url, filename)
         fields["log_url"] = log_url
+        if 'executor' in zuul and 'hostname' in zuul['executor']:
+            fields["zuul_executor"] = zuul['executor']['hostname']
         return fields