Start sprite animation at the beginning (#11509)

When setting a sprite animation, do not keep the last animation's frame number. Setting a new animation should start the animation at the start of the new animation.

src/client/content_cao.cpp

@@ -1722,6 +1722,7 @@ void GenericCAO::processMessage(const std::string &data)
 
 		m_tx_basepos = p;
 		m_anim_num_frames = num_frames;
+		m_anim_frame = 0;
 		m_anim_framelength = framelength;
 		m_tx_select_horiz_by_yawpitch = select_horiz_by_yawpitch;