test: Increase CAMComponent default spawn delay

The CI is currently spotting some failure on the test
"test_cam_app_multiple_stream", looking into the log the
cam-app-example fails immediately to send a stream event,
which might imply that the server is not ready yet to serve
the connections.

Increase the default delay to be waited after spawning the
cam-server.

Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>