drawTool在绘制point后调用禁用函数，会在禁用所在位置坐标下新生成一个point

[Wuli-Zhang]

maptalks's version and what browser you use?
---- 1.0.0-rc.14

Issue description
---- drawTool绘制任何图形都可以正常绘制。如果调用禁用函数（disable），那么绘制Point的时候会在禁用时候的鼠标在的坐标下生成一个Point；如果禁用函数在drawend监听回调函数内调用，则不会出现。
linestring和polygon都正常不会多绘制一个图形只有point会在上述情况下多绘制一个。

Please provide a reproduction URL (on any jsfiddle like site)

        mode: 'Point'
      }).addTo(this.map)
      this.drawTool.enable()
      const _vm = this
      this.drawTool.on('drawend', function (param) {
        if (!_vm.shapeDrawLayer) {
          _vm.shapeDrawLayer = new maptalks.VectorLayer('draw-layer').addTo(
            _vm.map
          )
        }
        _vm.shapeDrawLayer.addGeometry(param.geometry)
        param.geometry.setProperties({
          type: param.geometry.type,
          gid: param.geometry._internalId
        })
      //此时调用禁用，不会出现两个点图形。
          _vm.drawTool.disable()
       
      })

this.drawTool = new maptalks.DrawTool({
        mode: 'Point'
      }).addTo(this.map)
      this.drawTool.enable()
      const _vm = this
      this.drawTool.on('drawend', function (param) {
        if (!_vm.shapeDrawLayer) {
          _vm.shapeDrawLayer = new maptalks.VectorLayer('draw-layer').addTo(
            _vm.map
          )
        }
        _vm.shapeDrawLayer.addGeometry(param.geometry)
        param.geometry.setProperties({
          type: param.geometry.type,
          gid: param.geometry._internalId
        })
       // 延迟函数内，或其他地方调用disable，就会在图层多生成一个点位。
        setTimeout(() => {
          _vm.drawTool.disable()
        }, 1500)
      })