[ndk] Update catapult file with new android ndk root locate

Because of the android sdk managed by CIPD (see go/use-adjective-apis),
its deps repo ndk needs to be relocated to third_party/android_ndk.

Bug: 659808
Change-Id: I043f1358e27a067bf37e5aa65ef63104dcfb9bfd
Reviewed-on: https://chromium-review.googlesource.com/861332
Reviewed-by: John Budorick <jbudorick@chromium.org>