setcifsacl: fix verify_ace_sid

setcifsacl: fix verify_ace_sid

The current method of trying to convert a name to a password struct and
then back to a SID is just weird. It also doesn't seem to work correctly.

Instead, look for a '\\' in the string. If there isn't one then try to
convert it directly to a SID.

If there is a '\\' or the direct-to-SID conversion didn't work, then
use wbcLookupName to do the conversion directly to a SID instead.

Also, fix the error handling. These routines return a wbcErr, so we
should use their macros to check whether it worked or not.

Signed-off-by: Jeff Layton <jlayton@samba.org>