Negotiate and save preferred compression algorithms

New negotiate context (3) allows the server and client to
negotiate which compression algorithms to use. Add support
for this and save it off in the server structure.

Also now displayed in /proc/fs/cifs/DebugData (see below example
to Windows 10) where compression algoirthm "LZ77" was negotiated:

Servers:
Number of credits: 326 Dialect 0x311 COMPRESS_LZ77 signed
1) Name: 192.168.92.17 Uses: 1 Capability: 0x300067	Session Status: 1 TCP status: 1 Instance: 1

See MS-XCA and MS-SMB2 2.2.3.1 for more details.

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>