Fix Already have 1 record(s) with pnfsPath= ...

This patch (a modified version of http://rb.dcache.org/r/5671) addresses 

Already have 1 record(s) with pnfsPath= ...

error when transferring files to directories containing writetoken flag

(commit c9fcd4d1779cf2573328c66804df3e9458d25c74 on master)

        Ticket: 7888
        Acked-by: Al Rossi
        Target: trunk
        Request: 2.6
        Request: 2.2
        Require-book: no
        Require-notes: no