* Use SHA2-256 hash with prefix to upgrade the paths
* test the SHA1 upgrade to SHA256
* Remove hash identifier and the delimiter; use 's' instead
* Added API test to verify the correctness of the fix
* Fix broken test
* remove unneeded test
with a new endpoint '/sys/audit-hash', which returns the given input
string hashed with the given audit backend's hash function and salt
(currently, always HMAC-SHA256 and a backend-specific salt).
In the process of adding the HTTP handler, this also removes the custom
HTTP handlers for the other audit endpoints, which were simply
forwarding to the logical system backend. This means that the various
audit functions will now redirect correctly from a standby to master.
(Tests all pass.)
Fixes#784
