Fix a use of an uninitialized variable by makeing sure
that sctp_med_chunk_output() always initialized the reason_code
instead of relying on the caller.
The variable is only used for debugging purpose.
This issue was reported by Peter Bostroem from Google.

MFC after: 3 days


git-svn-id: svn+ssh://svn.freebsd.org/base/head@273634 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f