Cancel stagger after weapon release animations (bug #6869)

Fixes #6869 (closed). Assuming I understood the issue and assaulted guards in Morrowind.exe correctly. Edit: no, I didn't. Take 2.

The characters will stop staggering after finishing their attack (either a weapon attack or a spell attack). This fixes the abrupt transition to still playing upper body stagger animation... replacing it with an abrupt transition to idle.