fixes #37, button feature not updated when cfwd disabled

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4220 43c1dc8c-776e-4df2-8ef1-6e829299be21
add patch by diederik

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4221 43c1dc8c-776e-4df2-8ef1-6e829299be21