Fix for recycling key events when sending global button broadcast

When broadcasting several global key/button events in a short time,
old key events can be overwritten by later ones as they refer to
the same object which is recycled. This can cause issues for
applications, where the expected key event is overwritten and
never received.

For each new broadcast create a copy of the key event and use
that in the broadcast intent.

Test: Send repeated key event(s) that are defined in 'global_keys'
      and verify they are received as expected.
Change-Id: I074827792387b66a0ccf15a00bceee01275fb16f