Bug 1163893 - Encode artifact url for app deployments

Artifact url that contains special chars will be encoded and passed by
the user. By the time it reaches rails controller all params (including artifact url)
will be decoded and any subsuquent url parsing or retrieval using curl will fail.
This fix will encode the url again after apache/rails decoding to overcome the
limitation.

Shouldn't we add to the list of unsupported_artifact_urls in the test case to cover the specific case that was raised in the bug?