fix runtime issues for scripts

now, some script to update kernel-headers is not working.
because of wrong variable value and test codes.
so this issue is fixed.

Change-Id: Iffae9607858cc3c1c58fa24244be217b5a1ab06e
Clean up DNS proxying.

Remove code duplication and fall back to trying directly if the proxy
isn't available. With this, tests still work if netd is dead (perhaps
because you've run "adb shell stop", or because you're running on the host).

Bug: 18547878
Change-Id: Ia4a9aa18b1fc79e09735107246989fa7fc6c8455
Merge "Clean up DNS proxying."
Merge "fix runtime issues for scripts"