Removed the AST_BRIDGE_FLAG_SMART flag, resulting in working conference destroy, even with larger participant numbers and foreign channel types (like SIP). More testing is necessary, but it looks hopefull.

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4172 43c1dc8c-776e-4df2-8ef1-6e829299be21