skupper init does not validate site names

[bryonbaker]

Describe the bug
if you perform a skupper init --sitename 'On Prem', skupper init succeeds but the router enters crash loop backoff because a site name cannot have a space.

How To Reproduce
See above

Expected behavior
The skupper init should validate all inputs that could cause a router crash before it dpeloys the routers.

Environment details

• Skupper CLI: 1.6.0
• Platform: openshift

Additional context
Add any other context about the problem here.