Always play AVPlayer by setting the rate directly.
Always play AVPlayer by setting the rate directly.

Remove the previous method of observing when the player changed state and setting the rate afterward.
There is an issue in `resume(at:)` that resulted in `player.play()` being called, but a play status change either not happening or not being observed.  This meant that the rate was sometimes not set after play began with the default 1.0 rate.

edx/edx-app-ios,edx/edx-app-ios,edx/edx-app-ios,edx/edx-app-ios,edx/edx-app-ios,edx/edx-app-ios,edx/edx-app-ios