qa: update to newer Linux tarball

This should make newer gcc releases happier in their default configuration.
kernel.org is now distributing tarballs as .xz files so we change to that
as well when decompressing (it is supported by Ubuntu Precise so we should
be all good).

Fixes: #11758

Signed-off-by: Greg Farnum <gfarnum@redhat.com>
(cherry picked from commit 1ea3f47)

qa/workunits/kernel_untar_build.sh

@@ -2,12 +2,11 @@
 
 set -e
 
-#wget -q http://ceph.com/qa/linux-2.6.33.tar.bz2
-wget -q http://ceph.com/qa/linux-3.2.9.tar.bz2
+wget -q http://ceph.com/qa/linux-4.0.5.tar.xz
 
 mkdir t
 cd t
-tar jxvf ../linux*.bz2
+tar Jxvf ../linux*.xz
 cd linux*
 make defconfig
 make -j`grep -c processor /proc/cpuinfo`