Multiselect container misaligned on filtering with appendTo="body"

[wtospit]

In case of using multiselect with filtering and appendTo, when typing to filter the list, the container move to the upper left corner, This's because in ngAfterViewChecked() of multiselect component, it doesn't check appendTo property so the position is always calculated as a relative position, in this fix I just check if this.appendTo is used or not if so, it should calculate as absolute position instead.