Reapply "netatalk: Disable checking for dtrace"

If dtrace was detected on the host it would be enabled, even
though it's not available on the target.

Reapply commit 5497d31 which was unintentionally reverted in 1d3f779.
netatalk: fix modified configure
Merge pull request #625 from saintdev/for-upstream

Fix Asus modified netatalk configure v2