Don't rely on GLConsumer frame number in virtual camera

Sometimes the GLConsumer frame number is not set correctly
(depending on how one writes into the Surface) causing the virtual
camera render thread to get stuck. This change maintains an atomic
bool within the virtual camera service itself to check if the
first frame has been drawn.

Test: VdmHost + VdmClient
Test: CtsVirtualDevicesCameraTestCases
Bug: 381074653
Flag: EXEMPT minor bugfix
Change-Id: If108f4d8da4f52c9bea550d27f34c927d7622737