Add setvar variables on incoming call

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4921 43c1dc8c-776e-4df2-8ef1-6e829299be21
Unset global_conf_filename when file specified during reload could not be found. When using 'sccp reload device SEP' and a non-realtime device, the config file needs to be reloaded to notice any changes.

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@4922 43c1dc8c-776e-4df2-8ef1-6e829299be21