Mark prebuilt droiddriver libs as built with SDK

They are used by some apps built with SDK. Since such apps shouldn't
link to libs built without SDK, this is causing link-type check warning.
As the warning will turn into error soon, fixing the warning by
correctly marking the libs as sdk_version: "current".

The source code for the libs are done in master but they were until
lollipop and they were built with SDK then.

Bug: 69899800
Test: m -j droiddriver-0.9-prebuilt is successful
Test: m -j HarnessUiTestLib is successful and does not show any
link-type check warning

Change-Id: Icd9dbe95f7440f026efe24d07bfea10a8f163789