fixed tooltip for mirrored elements

[5ila5]

Tool-tips where not displayed at a mirrored widget but at its parent. This fixes this.

It's probably not a very elegant way. There may be a much better one but I wanted to make you aware of this issue while presenting my (hacky) way of fixing this

[elParaguayo]

Thanks for looking at this. I'm not convinced this is the right way to do this so I may took a look separately.

Also, I don't love mirrorer widgets in general and suspect they'll clash with a few things that qtile-extras adds.