[VOL-4054] pass the reboot command even with ONL hanging

Change-Id: I95749e018cb498d043215002278b145291fdc883
diff --git a/jjb/pipeline/voltha/master/physical-build.groovy b/jjb/pipeline/voltha/master/physical-build.groovy
index 4e89746..4a0a9d6 100644
--- a/jjb/pipeline/voltha/master/physical-build.groovy
+++ b/jjb/pipeline/voltha/master/physical-build.groovy
@@ -315,7 +315,7 @@
             timeout(15) {
               sh returnStdout: true, script: """
               ssh-keyscan -H ${deployment_config.olts[i].sship} >> ~/.ssh/known_hosts
-              sshpass -p ${deployment_config.olts[i].pass} ssh -l ${deployment_config.olts[i].user} ${deployment_config.olts[i].sship} 'rm -f /var/log/openolt.log; rm -f /var/log/dev_mgmt_daemon.log; rm -f /var/log/openolt_process_watchdog.log; reboot' || true
+              sshpass -p ${deployment_config.olts[i].pass} ssh -l ${deployment_config.olts[i].user} ${deployment_config.olts[i].sship} 'rm -f /var/log/openolt.log; rm -f /var/log/dev_mgmt_daemon.log; rm -f /var/log/openolt_process_watchdog.log; reboot -f > /dev/null &' || true
               sleep ${waitTimerForOltUp}
               """
             }