Use _FindAdb (cached) directly instead of Adb wrapper. A little simpler, no need to pass around an additional `apk` arg. Also fix missed _GetAdbRoot() call. Bug: angleproject:6854 Change-Id: Id64e5f35fb21a6aef7d99e614dc0eae753c24317 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3600912 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Roman Lavrov <romanl@google.com>