waiting explicitly after OLT reboots for evaluating test failures

Change-Id: I924953bae76d6d6b9483de3b7be4559f408e06fb
diff --git a/tests/functional/Voltha_FailureScenarios.robot b/tests/functional/Voltha_FailureScenarios.robot
index 6f773bd..26de016 100644
--- a/tests/functional/Voltha_FailureScenarios.robot
+++ b/tests/functional/Voltha_FailureScenarios.robot
@@ -136,6 +136,8 @@
     END
     # Wait for the OLT to come back up
     Wait Until Keyword Succeeds    120s    10s    Check Remote System Reachability    True    ${olt_ip}
+    # Waiting extra time for the ONUs to come up
+    Sleep    60s
     Run Keyword And Ignore Error    Collect Logs
     Run Keyword If    ${has_dataplane}    Clean Up Linux
     Wait Until Keyword Succeeds    ${timeout}    2s    Perform Sanity Test