Tidy up active tab styles to match background, border alignment on page tabs.

Before: https://www.evernote.com/shard/s6/sh/82f0a398-c80a-4cb7-81d7-a10b6e2c85ff/b1dfa1ae8ffcbd633b548fa3b2ea8951

After: https://www.evernote.com/shard/s6/sh/66cbe9d3-df0a-42c8-a6e8-a82c68161efe/27df7167802de9c3a267d40324972aa3

Tested throughout the CMS in IE8, Firefox and Chrome.