FreeSWITCH-FS-8767

Merge pull request #403 in FS/freeswitch from ~DRAGOS_OANCEA/freeswitch-dragos:opus-fix-plc-init to master

* commit 'ecabfc7f9a71b8ec17e1a0253d3811c08fbdcbce':
  FS-8005: mod_opus : fix for rare decoder error when doing PLC, OPUS_GET_LAST_PACKET_DURATION might return 0