e_comp_wl_input: allow cursor warping to hint position requested by inactive window

e_comp_wl_input: allow cursor warping to hint position requested by inactive window

In cases where active constraint window doesn't set its cursor hint position,
the cursor will be warped to the hint position provided by the inactive window
requesting it.

< Scenario >
1. The left edge window becomes locked.
2. To release the pointer lock, the left edge window requests warp_pointer,
without setting its cursor hint position.
3. The top edge window sets its cursor hint position because it expects
the cursor to appear from the top rather than the left side.

Change-Id: Ia4ee073bdc30e29d7a844c5c3bf542d46cd1c48c