ms-ice: legacy FINGERPRINT mode
In order to preserve compatibility with clients which use custom CRC
lookup table from [MS-ICE2], whenever a connectivity check request or
reply is sent, an additional message is sent along. These two messages
differ only in FINGERPRINT attribute - one uses regular CRC lookup table
for calculation, the other uses the modified table.
When a message is received and FINGERPRINT doesn't pass validation using
regular CRC table, the receiver also tries to verify using the modified
table.
[MS-ICE2] 3.1.4.8.2 describes this procedure.
The commit fixes compatibility with older MSOC and Lync clients.
Differential Revision: https://phabricator.freedesktop.org/D1138