NFSD: Refactor nfsd4_cleanup_inter_ssc() (2/2)

Move the nfsd4_cleanup_*() call sites out of nfsd4_do_copy(). A
subsequent patch will modify one of the new call sites to avoid
the need to manufacture the phony struct nfsd_file.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>