audit_logging: Remove debug log header and JSON Authentication: prefix

audit_logging: Remove debug log header and JSON Authentication: prefix

Feedback from real-world users is that they really want raw JSON
strings in the log.

We can not easily remove the leading "  " but the other strings above
and before the JSON are really annoying to strip back off

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13714

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>
(cherry-picked from edab1318f9138c0d87de7cc7cfa5da8e29c906f8 and modified
for v4-9 by Gary Lockyer)