In HTML documents with openstackdocstheme, vertical lines are shown
at the left side for literal blocks. Indented blocks are considered
as literal blocks in ReST text.
Unnecessary indented blocks are found in the glance document and
it leads to blocks with unexpected vertical left lines and
sometimes with unexpected fonts like [1].
Unexpected literal blocks are cleanup.
This commit also converts Definition lists in user/formats.rst and
user/common-image-properties.rst into the proper way in ReST text.
[1] https://docs.openstack.org/glance/latest/user/formats.html#container-format
Change-Id: I1b026f919bb22a59d23e3bb93bb7919d202a62fc
b6ceda28a4