Sort package only after null/bad elements have been removed.

Fixes a problem where the _CST sort was performed too early.  This
change sorts the package only after null/bad elements have been
removed.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>