Currently find_openstateowner_str look ups are done both in
nfsd4_process_open1() and alloc_init_open_stateowner() - the latter
possibly being a surprise based on its name.

It would be easier to follow, and more conformant to common patterns, if
the lookup was all in the one place.

So replace alloc_init_open_stateowner() with
find_or_alloc_open_stateowner() and use the latter in
nfsd4_process_open1() without any calls to find_openstateowner_str().

This means all finds are find_openstateowner_str_locked() and
find_openstateowner_str() is no longer needed.  So discard
find_openstateowner_str() and rename find_openstateowner_str_locked() to
find_openstateowner_str().
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>