Fixing bad package for StubSecurityGroupExtensionIntegrationTest
URL encode string to sign.

As recommended at
http://s3.amazonaws.com/doc/s3-developer-guide/RESTAuthentication.html:

"You can also send a signature as a URL-encoded query-string parameter
in the URL for the request."

Also deals with some of the craziness of URL encoding/decoding in
jclouds.

References JCLOUDS-200