With sudoers one may override default sudo user. This mostly works
provided the admin configured the replacement appropriately. However
there are exceptions that absolutely must be run by root such as
/usr/sbin/installer and, under certain circumstances, /bin/launchctl.
Unfortunately, the removal shell script introduced in #10860 does not handle paths very well that dont exist, e.g.
* `find` runs before its `-exec` test, thus throws `find: "${path}": No such file or directory`
* it seem that `/bin/rmdir` is intended to break is certain cases, thus `-f` is not desired.
so, if `${path}` does not exist, it'll still break, which is most likely not one of those cases.
This change reintroduces a check for existence. This way, it is ensured that there is actually
a directory to be removed when invoking the script.
