add checks to user update processing

[mattkasun]

Describe your changes

also addresses GRA-1480

Provide Issue ticket number if applicable/not in title

Provide testing steps

Checklist before requesting a review

• My changes affect only 10 files or less.
• I have performed a self-review of my code and tested it.
• If it is a new feature, I have added thorough tests, my code is <= 1450 lines.
• If it is a bugfix, my code is <= 200 lines.
• My functions are <= 80 lines.
• I have had my code reviewed by a peer.
• My unit tests pass locally.
• Netmaker is awesome.

[theguy951357]

will wait on changes

[theguy951357]

non-admin user cannot change the credentials of an admin user.
critical list passes