It was added in 81d338952d in an attempt to fix focus handling after
closing a floating window, but shortly after made redundant in
a551d1367c when we noticed it causes more harm than good. Unfortunately
it wasn't fully reverted, making the code more complex than necessary.
Drop the remaining bits.
Now it's almost obvious that the only difference between this and
X.L.StateFull.FocusTracking is the isF condition.
BTW the original issue 81d338952d was trying to fix can be fixed by
using X.H.RefocusLast, from the author of X.L.StateFull.FocusTracking.
:-)
Now TrackFloating remembers focus for the given layout when the other window is
also tiled, but not fed to the given layout: this helps with X.L.IM, among
others.
Addresses the comment that:
If the focus goes from the floating layer to tiling by deleting a floating
window, it's again the master window that gets focus, not the remembered
window.
