Disable _onZoomStart in canvas renderer

This fixes disappearing paths when starting an animated zoom.

src/layer/vector/Canvas.js

@@ -25,6 +25,8 @@ L.Canvas = L.Renderer.extend({
 		this._ctx = container.getContext('2d');
 	},
 
+	_onZoomStart: L.Util.falseFn,
+
 	_update: function () {
 		if (this._map._animatingZoom && this._bounds) { return; }