ZOOKEEPER-3896: PollSCM hourly only to let previous builds to finish

Looks like that PollSCM trigger will trigger another build on the same ref if other builds haven't completed rather than haven't started.

I change the polling interval to hourly to let other builds finish in time.

Author: Andor Molnar <andor@apache.org>

Reviewers: Enrico Olivelli <eolivelli@apache.org>

Closes #1413 from anmolnar/ZOOKEEPER-3896_2

Jenkinsfile

@@ -21,10 +21,11 @@ pipeline {
 
     options {
         buildDiscarder(logRotator(daysToKeepStr: '14'))
+        timeout(time: 59, unit: 'MINUTES')
     }
 
     triggers {
-        pollSCM 'H/10 * * * *'
+        pollSCM('@hourly')
         cron('@daily')
     }
 
@@ -68,4 +69,3 @@ pipeline {
         }
     }
 }
-