integrity: Always reference the blacklist keyring with appraisal

Commit 273df864 ("ima: Check against blacklisted hashes for files with
modsig") introduced an appraise_flag option for referencing the blacklist
keyring.  Any matching binary found on this keyring fails signature
validation. This flag only works with module appended signatures.

An important part of a PKI infrastructure is to have the ability to do
revocation at a later time should a vulnerability be found.  Expand the
revocation flag usage to all appraisal functions. The flag is now
enabled by default. Setting the flag with an IMA policy has been
deprecated. Without a revocation capability like this in place, only
authenticity can be maintained. With this change, integrity can now be
achieved with digital signature based IMA appraisal.

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Reviewed-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>