MFC r303199:

ctld(8): Fix MaxBurstLength negotiation.

The target must reply with the selected value of MaxBurstSize instead of
just echoing back the initiator's offered value.

Reviewed by: mav@
Approved by: re@ (gjb@)
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D7278