Prepare for enabling H302 rule (api/compute)

We can use H302 rule but ignore it now. This commit prepares for
enabling H302 rule. But this commit modifies tempest/api/compute only
and excludes some violations[1] because if we fix all of them at one
time, it's hard to merge this commit.

[1]
 tempest.test.attr
 tempest.common.rest_client.RestClient
 tempest.common.rest_client.RestClientXML
 tempest.services.compute.xml.common.xml_to_json
 tempest.services.compute.xml.common.Element
 tempest.services.compute.xml.common.Document
 tempest.services.compute.xml.common.Text
 tempest.services.compute.xml.common.XMLNS_11
 tempest.services.compute.xml.common.XMLNS_V3
 tempest/clients.py

Change-Id: I582d72543f83e01fe3b9cfa9f7132dfdd36a2225
Prepare for enabling H302 rule (common,services,stress)

We can use H302 rule but ignore it now. This commit prepares for
enabling H302 rule. But this commit modifies tempest/{common, services,
stress} only and excludes some violations[1] because if we fix all of
them at one time, it's hard to merge this commit.

[1]
 tempest.test.attr
 tempest.common.rest_client.RestClient
 tempest.common.rest_client.RestClientXML
 tempest.services.compute.xml.common.xml_to_json
 tempest.services.compute.xml.common.Element
 tempest.services.compute.xml.common.Document
 tempest.services.compute.xml.common.Text
 tempest.services.compute.xml.common.XMLNS_11
 tempest.services.compute.xml.common.XMLNS_V3
 tempest/clients.py

Change-Id: Ia68d8bb8e8a64944357d3879832b70947646266b
Merge "Prepare for enabling H302 rule (common,services,stress)"