Skip namespace mangling

Historically, Sling needed to escape JCR namespaces from URL paths, since the ":" character posed a problem for older browsers. However, RFC 3986 [0] allows the colon in path segments and all current browsers don't have an issue with this for years.

The XSSAPI implementation currently present in Sling attempts to mangle JCR namespaces, but without any knowledge of the actual registered namespaces. Given that colon is not really a problem any more and that resource paths should anyways be passed through the org.apache.sling.api.resource.ResourceResolver#map(java.lang.String) API before being exposed as URLs, the code that attempts to perform mangling in the XSSAPI#getValidHref implementation should be removed.

For more details consult the dev list [1].

[0] - https://tools.ietf.org/html/rfc3986
[1] - https://s.apache.org/4ga5i