subtests.docker_cli.dockerinspect: Check CamelCase

This patch adds the CamelCase keys check into the
docker_cli/dockerinspect/inspect_all test.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Merge pull request #380 from ldoktor/inspect

subtests.docker_cli.dockerinspect: Check CamelCase