Description clean-up for volume actions

Some minor description clean-ups for volume action
'change volume type' and 'upload to image' to remove
'From here you can'.

Also remove unecessary 'required=True' for the field.

Closes-Bug: #1364623

Change-Id: Ia8c1a593e80abf193f26f7cb97bc1ba383383399
Merge "Description clean-up for volume actions"