FFmpeg: QCamera::FlashOn is unreliable

When using QCamera::FlashOn, flash mode is unreliable and causes problematic side-effects.

This issue is a bit flaky to reproduce but generally, when taking multiple image-captures, with a few seconds in between, with flash forced on,  the camera-capture will become unresponsive and QImageCapture::onImageSaved is never called. In this case, it does not help to call QImageCapture::captureToFile multiple times.

I have observed multiple strange side-effects in this scenario, all happening seemingly undeterministically. In some cases, the auto-focus will stop working and be hard-locked to the focus distance where the image-capture began, even if I'm using QCamera::FocusModeAuto. In some cases, the flash can be left on permanently. In some cases, you can force the image-capture to finish without any flash if you set QCamera::setFlashMode(QCamera::FlashOff), but this is not consistent.

I have included the test-project that I use internally to test functionality, but this should apply to all apps.

Steps to reproduce:

1. Have an Android device with a physical flash
2. Set QCamera::setFlashMode(QCamera::FlashOn) (Default in the provided project)
3. Point camera at the distance
4. Call QImageCapture::captureToFile / Press "Capture" in the provided project (Even this step will sometimes lock up)
5. When capture is finished, point camera at a close object
6. Call QImageCapture::captureToFile / Press "Capture" in the provided project

Please perform the steps multiple times to confirm.

What do you expect to happen:

I expect each to call to QImageCapture::captureToFile() to result in an individual image with flash forcefully applied. I expect the camera to return to using auto-focus if I'm using QCamera::FocusModeAuto. If the camera is unable to adjust any properties correctly, I expect to get an out-of-focus image but with flash applied.