chkconfig-alternatives: drop default preference

We want to prefer the existing behavior of use of chkconfig when no preference
is explicitly defined by the user.

Signed-off-by: Christopher Larson <kergoth@gmail.com>
isolated-sstate-dir: only enable if ISOLATED_SSTATE_DIR != SSTATE_DIR

Signed-off-by: Christopher Larson <kergoth@gmail.com>