IMS-VT: Auto fullscreen issues during UI rotation.

- Sometimes auto enter full screen runnable scheduled before
InCallActivity re creation can fire and force full screen
mode when voice call is ongoing. This can happen during VT to
Voice transition during call modify or SRVCC.
Clear pending runnable in onUiUnready to prevent this.
- Consider case where VT call UI is in fullscreen mode and the
UI orientation is changed. When InCall activity is re created
due to rotation, the fullscreen flag is still true, but actual
UI will be created in normal mode. Due to wrong fullscreen flag
value, auto enter fullscreen thread is not scheduled.
To fix this clear fullscreen flag in InCallActivity.onCreate().

Change-Id: Ic3f35aeec95e662d2fab5b3dc7bb41d813fb39b6
CRs-Fixed: 1012878 979860