kbd-util: fix use of ERRNO_IS_RESOURCE()

kbd-util: fix use of ERRNO_IS_RESOURCE()

Given that ERRNO_IS_RESOURCE() also matches positive values,
make sure this macro is not called with arguments that do not have
errno semantics.

In this case the argument passed to ERRNO_IS_RESOURCE() is the value
returned by recurse_dir_at() which can legitimately return positive
values without errno semantics, so fix this by moving the ERRNO_IS_RESOURCE()
invocation to the branch where the return value is known to be negative.