nfscl: Add optional support for slots marked bad

This patch adds support for session slots marked bad
to nfsv4_sequencelookup(). An additional boolean
argument indicates if the check for slots marked bad
should be done.

The "cred" argument added to nfscl_reqstart() by
commit 326bcf9394c7 is now passed into nfsv4_setquence()
so that it can optionally set the boolean argument
for nfsv4_sequencelookup(). When optionally enabled,
nfsv4_setsequence() will do a DestroySession when all
slots are marked bad.

Since the code that marks slots bad is not yet committed,
this patch should not result in a semantics change.

PR: 260011
MFC after: 2 weeks