Add a new secret type known as "passphrase" - it will handle adding the
secret objects that need a passphrase without a specific username.

The format is:

   <secret ...>
     <uuid>...</uuid>
     ...
     <usage type='passphrase'>
       <name>mumblyfratz</name>
     </usage>
   </secret>
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>