Simplify EVS HAL and move to "agressive opens"

This adapts the API implementation to allow a duplicate "open" operation
to automatically close any previous connections to the device.  This
works around a binder level issue that can cause destructors triggered
by remote clients to be delivered out of order to the server.

This was originally change ag/1969959 on master, but has been
recreated on oc-dev (cherry-picking was broken at the time).
The original master change will be abandoned in favor of this getting
merged down from oc-dev.

Test:  Run Vts test (added in following change)
Change-Id: I7b417998e59a4d592fbb91811c4101f39097c5dd