Check crossover session earlier, before creating anything new

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5200 43c1dc8c-776e-4df2-8ef1-6e829299be21
Only check pbx_channel_pbx during force and request hangup

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5201 43c1dc8c-776e-4df2-8ef1-6e829299be21