tpl_wayland_egl_thread: Added assert case to detect abnomalies.

tpl_wayland_egl_thread: Added assert case to detect abnomalies.

 - In the twe thread, the event fd being poll must be
  woken up only with G_IO_IN.
 - However, if some problem occurs in fd, it can wake up with
  G_IO_ERR, G_IO_HUP, G_IO_NVAL, and try dispatch.
   In this case, it is difficult to predict the situation after G_SOURCE_REMOVE,
  so ASSERT should be used to find the time when the problem occurs.
 - If there is no ASSERT () or remove, g_main_loop will repeatedly
  wake up and try to dispatch the source, causing a problem of making CPU usage high.

Change-Id: I678119c192c7ab52acd11965e54dfa9a890fa8e7
Signed-off-by: Joonbum Ko <joonbum.ko@samsung.com>