HBASE-27425 run flaky test job once an hour. (#4828)

Signed-off-by: Peter Somogyi <psomogyi@apache.org>
Signed-off-by: Duo Zhang <zhangduo@apache.org>
(cherry picked from commit c8e2d80)

dev-support/flaky-tests/run-flaky-tests.Jenkinsfile

@@ -21,7 +21,7 @@ pipeline {
     }
   }
   triggers {
-    cron('H H/4 * * *') // Every four hours. See https://jenkins.io/doc/book/pipeline/syntax/#cron-syntax
+    cron('@hourly') // See https://jenkins.io/doc/book/pipeline/syntax/#cron-syntax
   }
   options {
     // this should roughly match how long we tell the flaky dashboard to look at