report: encode XML Character Entities in xUnit report

report: encode XML Character Entities in xUnit report

Since the xUnit report is an XML document, special XML characters such
as '<', '>', '&', etc. have to be encoded as "&lt;", "&gt;", etc.
Otherwise programs parsing something like this:

	<testcase classname="xfstests.global" name="generic/450" time="0">
		<skipped message="Only test on sector size < half of block size" />
	</testcase>

Will get choke the unescaped '<' character in the skipped message.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: Dmitry Monakhov <dmonakhov@openvz.org>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>