fgt_asg: changing admin password breaks asg

[bartekmo]

Cloud Function of fgt_asg_with_function module relies on the admin password for authenticating against asg members' API. Changing the admin password makes the function to stop working and fail updating FGSP peer list or re-electing new primary.

Additionally, the password is visible in plain text in multiple places in the logs typically revealing it to all users of the project.

I suggest using API token added to bootstrap configuration and kept secret from the logs.