xrootd: Upgrade to xrootd4j 1.2.5

Fixes spec compliance issues related to null-terminated strings.
Affects the locate, login and open responses.

Target: 2.8
Request: 2.7
Request: 2.6
Require-notes: yes
Require-book: no
Acked-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Patch: http://rb.dcache.org/r/6678/
(cherry picked from commit 191ef0c45de7df148b8e4a09ec4d7d48213f7c16)
Merge pull request #453 from gbehrmann/fix/2.7/rb6678

xrootd: Upgrade to xrootd4j 1.2.5