Test for Bugzilla Bug 86885: CSS2.1 failure: border-conflict-element021a.

When two adjacent table row groups (thead, tbody, tfoot) have the same border-width and the same border-style in a 'border-collapse: collapse' table, then the color of the border from the topmost table row group wins: so, a thead wins over a tbody which wins over tfoot.

This test verifies the aforementioned sceanario when more than one header and/or footer is specified. The first thead specified in the page should be rendered at the top of the table; similarly the first tfoot specified in the page should be rendered as the last section of the table. In this case both the top-most and the bottom-most sections should be displayed in green color. Also, there should be no overlap of border-colors at the corners.