MFS: r366050, r366117
Fix a LOR between the NFS server and server side krpc.

Recent testing of the NFS-over-TLS code found a LOR between the mutex lock
used for sessions and the sleep lock used for server side krpc socket
structures.
The code in nfsrv_checksequence() and nfsrv_bindconnsess() would call
SVC_RELEASE() with mutex(es) held. Normally this is ok, since
all that happens is SVC_RELEASE() decrements the reference count.
However, if the socket has just been shut
down, SVC_RELEASE() drops the reference count to 0 and acquires a sleep
lock during destruction of the server side krpc structure.

This patch fixes the problem by moving the SVC_RELEASE() call in
nfsrv_checksequence() and nfsrv_bindconnsess() down a few lines to
below where the mutex(es) are released.

Approved by: re (gjb)