Temporarily default signature version in blobstore configuration to "2".
Temporarily default signature version in blobstore configuration to "2".

Works around a bug in the s3cli which does not properly handle unset
signing version information.

[#111994203](https://www.pivotaltracker.com/story/show/111994203)

cloudfoundry-incubator/bosh-openstack-cpi-release,cloudfoundry-incubator/bosh-openstack-cpi-release,cloudfoundry-incubator/bosh-openstack-cpi-release