One test wants to make sure thead, tfoot and tbody will have th/td's
with the same size/number.
Existing test for tbody was retrieving the grouped td, which has a
colspan of 100%. Note that this 100% value seems to be wrong as it is
interpreted like "100" by the browser. We do not want to test this row
anyway, but the real row, the one with all the td's.
This patch makes it retrieve the second tr and count the number of td it
has.
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>