Fixes Register a system and validate subscription tab and some timing issues

[kbidarkar]

I realized that sleep is required due to timing issues, if we have a better solution, please let me know.

[kbidarkar]

check-for-success notification checks for notification, but the notification for some reason is not reliable and hence changed the logic to verify it.

Hope this fixes many of the manifest test timing issues which had causes the failures.

[sghai]

ACK