ipc: Start host channel handshake earlier

BrowserChildProcessHostConnected notification, that's executed by
the runner loop, is too late as well to start the GPU and browser
process handshaking.

Signed-off-by: Tiago Vignatti <tiago.vignatti@intel.com>

The patch was imported from https://github.com/tiagovignatti/ozone-wayland/
as of commit id 6922a29.

1)Revert changes related to EstablishChannel.
2)Ensure ChannelConnected flag is set properly. This would ensure
  that we don't add host as filter more than once.

Signed-off-by: Kalyan Kondapally <kalyan.kondapally@intel.com>
Update OzoneProcessObserver documentation.