Turn off camera access when not required

[JessicaJHee]

As a result of this https://github.com/Lenscrafters-Capstone/LensCrafters-free/pull/37, the camera access is requested from the beginning of the workflow. Ideally, we want the camera access to be only requested when the try-on pop-up is opened, and turn off the access when the pop-up is closed.

[o-farag]

@JessicaJHee iirc this PR fixes this? https://github.com/Lenscrafters-Capstone/LensCrafters-free/pull/41 If so let's close the issue

[JessicaJHee]

At the moment it requests when the try-on window is first opened, but it will not pause the camera if the window is closed. I couldn't get the pause API to work, so if you think it's fine the way it is, we can close it.