smbd: Introduce close_file_smb()

smbd: Introduce close_file_smb()

This does almost everything that close_file_free() does, but it leaves
the fsp around.

A normal close_file() now calls fsp_unbind_smb() twice. Functionally
this is not a problem, fsp_unbind_smb() is idempotent. The only
potential performance penalty might come from the loops in
remove_smb2_chained_fsp(), but those only are potentially large with
deeply queued smb2 requests. If that turns out to be a problem, we'll
cope with it later. The alternative would be to split up file_free()
into even more routines and make it more difficult to figure out which
of the "rundown/unbind/free" routines to call in any particular
situation.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>