procps: fix for base_sbindir == sbindir

procps: fix for base_sbindir == sbindir

An rmdir call in do_install_append was trying to remove the
sbindir, however in a system with a merged usr this directory
is not empty and therefore failing to rm it causes an ERROR.

Instead check that sbindir != base_sbindir before trying to
remove the directory.

Signed-off-by: Joshua Lock <joshua.lock@collabora.co.uk>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>