Replace external/okhttp path to new repository android_external_okhttp

Change-Id: I7de913d0d4be586ba41bda8dbda074e1bd98b085
Merge branch 'android-4.4' of https://github.com/omnirom/android into android-4.4
[test] android_external_skia from android-legacy

Change-Id: I5e707bb6d7bee2f835bfe57340e9307f062ef138