erdtlsagent: Use g_once instead of a manual static mutex
erdtlsagent: Use g_once instead of a manual static mutex

deepikateriar/openwebrtc-plugins-0.8,ossy-szeged/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.80,ossy-szeged/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.80,ossy-szeged/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.8,deepikateriar/openwebrtc-plugins-0.80,EricssonResearch/openwebrtc-gst-plugins,ford-prefect/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.8,ford-prefect/openwebrtc-gst-plugins,EricssonResearch/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.80,ford-prefect/openwebrtc-gst-plugins,ossy-szeged/openwebrtc-gst-plugins,sancane/openwebrtc-gst-plugins,EricssonResearch/openwebrtc-gst-plugins,ford-prefect/openwebrtc-gst-plugins,sancane/openwebrtc-gst-plugins,sancane/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.8