Fixes nothing is displayed if volume metadata is empty problem

If volume metadata is empty, nothing is displayed below "Metadata"
<h4> heading in the volume detail page. So, this patch fixes this
problem by displaying "None".

Change-Id: I0302e47cc8c9e471972ef7c249d54582242b5390
Closes-bug: #1382876
Merge "Fixes nothing is displayed if volume metadata is empty problem"