Fix issue with incorrect determination of whether or not a string is encoded
by replacing URLDecoder with import org.springframework.web.util.UriUtils
as the former does not handle '+' character.

    Ticket: #8356
    Acked-by: Albert Rossi <arossi@fnal.gov>
    Target: trunk
    Request: 2.9
    Request: 2.8
    Request: 2.7
    Request: 2.6
    Require-book: no
    Require-notes: yes

RELEASE NOTES

Fix bug effecting ability to stage files from Enstore if file names
contain '+' character.