Stop using 5iveL!fe

What does this Merge Request do?

The proposal here is to not use 5iveL!fe as the default root password, but rather create a random password for each developer.

gdk reconfigure will create a ./gitlab/.root_password file with this random value.

Once this gets merged, we will create a follow-up MR on GitLab side to seed the password from the file instead of hardcoding 5iveL!fe.

Please see this issue description and following discussion for the reasoning behind it.

/cc @mdewji

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.