Camera: Wait for UI focus during GL legacy testing

Cts test case #testCameraToSurfaceTextureMetadata seems to
occasionally fail due to 'keyDispatchingTimedOut' that is
likely caused by some random delay in the main UI thread.
Avoid the possible input timeout by waiting for the app to
receive focus before triggering the test setup sequence.

Bug: 207569395
Test: Camera CTS
Change-Id: I46f1130d4aba25d15095abd1592b95a8c6600df9
1 file changed