os/chain_listxattr: fix leak fix

e22347df3854a5c5ebc6631c62d70447d67d722d added a bad goto; just free
explicitly instead.

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Noah Watkins <noahwatkins@gmail.com>
Merge remote-tracking branch 'origin/next-fix' into next

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>