The standalone execution of upload-certs phase does not print
the key that that user should use for the newly uploaded encrypted
secret. Print this key in the upload-certs phase in both
standalone mode or if executed in the standard init workflow.

Make it possible to omit the printing if the user passes
--skip-certificate-key-print.

Also:
- Uppercase string in Printf call in copycerts.go
- Don't use V(1) for the "Skipping phase" message in uploadcerts.go
instead always print a message that the user case use
--experimental-upload-certs. This solves a problem if the user tried
the standalone phase but didn't pass --experimental-upload-certs.