Decrease cache sync time in inspector discovery job

We are deleting node from ironic for simulate node discovery,
so it's possible race when node cache become inconsistency.

This change decrease period time from default 60 to 5 sec to avoid
cache inconsistency.

Change-Id: I6af4dc6acebb673d256940278ca94a657774cdf9

jenkins/jobs/ironic.yaml

@@ -146,6 +146,9 @@
                  export DEVSTACK_GATE_REMOVE_STACK_SUDO=0
                  # enable enroll hook
                  export DEVSTACK_LOCAL_CONFIG+=$'\n'"IRONIC_INSPECTOR_NODE_NOT_FOUND_HOOK=enroll"
+                 # we are deleting node from ironic for simulate node discovery,
+                 # so inspector has to sync cache asap
+                 export DEVSTACK_LOCAL_CONFIG+=$'\n'"IRONIC_INSPECTOR_CLEAN_UP_PERIOD=5"
             fi
 
 - builder: