cursor: fix focus when menu is closed by clicking its border

cursor: fix focus when menu is closed by clicking its border

Before this commit, the pointer focus is cleared when a menu is closed
by clicking its border. This is because get_cursor_context() returns
type=LAB_SSD_NONE when the cursor is on the menu border and
cursor_update_common() clears the pointer focus. This commit fixes this
by replacing cursor_update_common() with cursor_update_focus(), which
calls get_cursor_context() again after the menu scene-node is hidden.