Make sequence numbers checks more strict.

While we don't support MCS, hole in received sequence numbers may mean
only PDU loss.  While we don't support lost PDU recovery, terminate the
connection to avoid stuck commands.

While there, improve handling of sequence numbers wrap after 2^32 PDUs.

MFC after:	2 weeks


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275864 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f