Fixes Speakerphone dropping (references #172)

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5067 43c1dc8c-776e-4df2-8ef1-6e829299be21
Fix sccp_sk_endcall on sharedline calls when call is connected

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5068 43c1dc8c-776e-4df2-8ef1-6e829299be21
move rtp_destroy to channel destruction

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5070 43c1dc8c-776e-4df2-8ef1-6e829299be21