Wait keystone_fernet running before init tokens

Init fernet task fails if keystone_fernet container
is not running and ssh port bind.
This change add a check to ensure all keystone_fernet containers
are running before init fernet tokens.

Change-Id: Ib95bb5a47a9174f1a00b82cc8b697c0dc19c848e
Closes-Bug: #1704758