[SCSI] libfcoe: update FIP FCF D flag from advertisments

Allow the D flag (indicating that keep-alives are not needed) to
be updated dynamically from received FIP advertisements.

Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>