LU-2922 changelog: recommend e2fsprogs-1.42.6.wc2

This patch updates lustre/ChangeLog to recommend
a newer e2fsprogs-1.42.6.wc2 release instead of the
old 1.41.90.wc4 version.

Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: Ib56092500545f0373a307d7645d41d91079ae086
Reviewed-on: http://review.whamcloud.com/5718
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>