(QE-588) vcloud_pooled: undefined method `request_uri'

- ensure that a scheme is defined for the vcloud pooling api uri
- if no scheme is defined the uri returned is a simple uri object that
  does not support the 'request_uri' method
Merge pull request #85 from anodelman/fix-uri

(QE-588) vcloud_pooled: undefined method `request_uri'