set mod_dahdi_codec dahdi transcoding device sockets to non-blocking to avoid hanging when there is no data and just return 0 bytes frame
Jira: MODCODEC-8


git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@13257 d0543943-73ff-0310-b7d9-9358b9ac24b2