compositor/window-drag: Fix keyboard resize
Both GRAB_OP_KEYBOARD_MOVING and GRAB_OP_KEYBOARD_RESIZING_* are defined as GRAB_OP_WINDOW_BASE with FLAG_KEYBOARD set, but the latter have additional bits set to indicate the direction.
That is, the GRAB_OP_KEYBOARD_MOVING bitmask cannot be used to differentiate between move- and resize operations. Instead, check whether any direction bits are set.
Fixes #2684