floating_enable: change reassign logic

floating_enable: change reassign logic

This allows the floating container's top left corner to be mapped
outside any output as long as they are contained partially by one. This,
for example, will allow:
mpv --geometry +1+1 video.mp4

For windows mapped to (0, 0) see comment in floating.c:270-273:
/* Some clients (like GIMP’s color picker window) get mapped
 * to (0, 0), so we push them to a reasonable position
 * (centered over their leader) */

 The floating_reassign_ws call is removed since we try to place the new
 floating container in the current output:
 /* Sanity check: Are the coordinates on the appropriate output? If not, we
  * need to change them */

Fixes #1341