[VOL-4267] Re-enabled RestartOpenOnuPingDt and RestartOpenOltPingDt scenarios with some modifications

Change-Id: Ie6098140524c3d2f5a9c9720e743b47d7824c480
diff --git a/libraries/utils.robot b/libraries/utils.robot
index 1c3b9ae..adcd9b2 100755
--- a/libraries/utils.robot
+++ b/libraries/utils.robot
@@ -1337,7 +1337,7 @@
     ...    ${container_type}=${None}    ${container_name}=${None}
     [Documentation]    Runs the 'ping' on remote system in background and stores the result in a file
     ${result}=    Login And Run Command On Remote System
-    ...    ping -I ${iface} ${dst_ip} > ${output_file} &
+    ...    echo "ping -I ${iface} ${dst_ip} > ${output_file} &" > ping.sh; chmod +x ping.sh; ./ping.sh
     ...    ${ip}    ${user}    ${pass}    ${container_type}    ${container_name}
     Log    ${result}