evas-wayland-shm: Use wl_display_dispatch_pending to wait for buffers

Summary: This fixes T2625 where launching filemanager would cause a
deadlock. The issue here is that wl_display_dispatch actually uses
poll() which will block and wait, while using
wl_display_dispatch_pending does not case any blocking.

Signed-off-by: Chris Michael <cp.michael@samsung.com>

src/modules/evas/engines/wayland_shm/evas_shm.c

@@ -419,7 +419,7 @@ _evas_shm_surface_wait(Shm_Surface *surface)
              if (surface->leaf[i].valid) return &surface->leaf[i];
           }
 
-        wl_display_dispatch(surface->disp);
+        wl_display_dispatch_pending(surface->disp);
      }
    return NULL;
 }