doc: correctly index the disk-image-create calls

Previously the, disk-image-create calls were not in verbatim
block.

disk-image-create -o bootstrap vm boot-stack ubuntu
disk-image-create -o ubuntu ubuntu

were converted to.

disk-image-create -o bootstrap vm boot-stack ubuntudisk-image-create
-o ubuntu ubuntu

The \n were lost.

This patch moves the disk-image-create calls in blockquote
paragraph.

Change-Id: Ie408071f78e764fe2f4f6987eb37e86da82bcd5e
Merge "doc: correctly index the disk-image-create calls"