0021431: Tidy up error handling in cert generator

Migrated from: https://tracker.clearos.com/view.php?id=21431

Reported by: PBaldwin

cert generator (/usr/sbin/system-certs) should have improved error handling and better output handling.

Noisy output example -- when the tool detects an invalid certificate, it will spit out something like:

   unable to load Private Key
  1234:error:0906D064:PEM routines:PEM_read_bio:bad base64 decode:pem_lib.c:829:

Error handling example -- though "system-certs" is intended for install scripts, command should provide help and guidance for those sysadmins who may run it manually.