useradd: Fix useradd do_populate_sysroot dependency bug

useradd: Fix useradd do_populate_sysroot dependency bug

If a task is adde which has a dependency on the do_populate_sysroot task of
the recipe, it will cause it to be installed into the sysroot (similar to
do_addto_recipe_sysroot). This fails since the postinst script is an overlapping
file:

Exception: FileExistsError: [Errno 17] File exists:
'tmp/sysroots-components/all/useraddbadtask/usr/bin/postinst-useradd-useraddbadtask'
  ->
'tmp/work/all-poky-linux/useraddbadtask/1.0/recipe-sysroot/usr/bin/postinst-useradd-useraddbadtask'

The copy written out at do_prepare_recipe_sysroot time is just for debug so
rename it, meaning there are no longer overlapping files and the installation
can be successful, removing the error.

[YCOTO #14961]

With the bug fixed, enable the test.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>