Update judgement of whether newest_release is dev

The format of Bosh Dev Release version has been changed:
new:https://github.com/cloudfoundry/bosh/blob/master/bosh_common/lib/common/version/release_version.rb#L15
old:https://github.com/cloudfoundry/bosh/blob/master/bosh_common/lib/common/version/release_version.rb#L26
In terms of  compatibility, check whether the release include “dev”.