Treat seinfo=default name=<anything> as an error.

check_app already checks for usage of name= entries
in seapp_contexts with no seinfo= specification to
link it back to a signer in mac_permissions.xml.
However, one can avoid this error by specifying
a seinfo=default which merely matches the default
stanza of mac_permissions.xml without actually ensuring
that it is tied to a specific certificate.  Catch
that error case too.

Change-Id: If33cf21501e8bfee44d31c92b6341dfa583552b2
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>