Ceph-qa: change the fsx.sh to support hole punching test

This patch change the fsx.sh to pull better fsx.c from xfstests site
to support hole punching test.

Signed-off-by: Yunchuan Wen <yunchuanwen@ubuntukylin.com>
Signed-off-by: Li Wang <liwang@ubuntukylin.com>