xrootd: Upgrade to xrootd4j 1.2.2

Fixes compatibility issues with xrootd plugins.

Target: trunk
Request: 2.7
Request: 2.6
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6233
(cherry picked from commit 9904943dcd20692379e4408a977ee78532813b3a)
Merge pull request #290 from gbehrmann/fix/2.7/rb6233

xrootd: Upgrade to xrootd4j 1.2.2