report: encode cdata sections correctly

report: encode cdata sections correctly

The XML report format captures the contents of .full and .out.bad files
in CDATA sections.  CDATA sections are supposed to be a stream of
verbatim data, terminated with a "]]>".  Hence XML entities such as
quotation marks and angle brackes should not be escaped, and an actual
bracket-bracket-gt sequence in those files /does/ need escaping.

Create a separate filtering function so that these files are encoded
properly.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>