Prepare for enabling H302 rule(services/compute/v3/json)

Currently H302 rule is ignored by tox. However, this rule should
be enabled. This patch partially fixes this problem to prepare for
H302 rule.

Change-Id: I4f573cb306f86cf8476f8fa8950a47c21e443db8
Merge "Prepare for enabling H302 rule(services/compute/v3/json)"