Update http_image config option to use latest image

`http_image config` option of `image` section is still referring
to old cirros image `cirros-0.3.1-x86_64-uec.tar.gz`.

Updated it to use new cirros image `cirros-0.6.2-x86_64-uec.tar.gz`.

Change-Id: I55e2fbd062c476e839fe8404bae18e918e745bc5
2 files changed