add external URL for cert logo image
add external URL for cert logo image

bigdatauniversity/edx-platform,bigdatauniversity/edx-platform,cognitiveclass/edx-platform,cognitiveclass/edx-platform,bigdatauniversity/edx-platform,cognitiveclass/edx-platform,bigdatauniversity/edx-platform,cognitiveclass/edx-platform,cognitiveclass/edx-platform,bigdatauniversity/edx-platform