fix "encoding problem in uPortal" with mod-shib2 SP

https://wiki.shibboleth.net/confluence/display/SHIB2/NativeSPAttributeAccess#NativeSPAttributeAccess-Tool-SpecificExamples for java says:
> Shibboleth attributes are by default UTF-8 encoded.
> However, depending on the servlet contaner configuration they are interpreted as ISO-8859-1 values.
> This causes problems with non-ASCII characters.
> The solution is to re-encode attributes

cf http://jasig.275507.n4.nabble.com/encoding-problem-in-uPortal-4-td4658322.html