camera (v)ndk: Setup vendor tags if they're not already, while calling getCameraService()

It is possible that by the time CameraManagerGlobal::getCameraService()
is called, cameraservice is up, however camera HAL providers haven't
registered themselves with cameraservice. In this case, the vendor tag
cache will not be available. As a result, we should check and set it up while
checking for cameraserver validity for subsequent calls of
CameraManagerGlobal::getCameraService().

Bug: 368235553

Flag: EXEMPT BUGFIX

Test: Vendor service which comes up before camera HAL registers itself
      with cameraserver can eventually, retrieve vendor tags.

Change-Id: I51ea31c11692498f1c07d7efdc91e4b176f73f27
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>