remove double release device

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4108 43c1dc8c-776e-4df2-8ef1-6e829299be21
use sccp_socket_stop_sessionthread in sccp_socket_device_thread_exit

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4109 43c1dc8c-776e-4df2-8ef1-6e829299be21