Workaround for a chrome bug where active pseudo class stays on inactive elements

Chrome has a nice bug where clicking on block element
inside an inline element will force the inline element
to keep the :active pseudo class.
this causes tooltips to stay open since our tooltips
show if the tooltip element has the :active pseudo class
a bug has been filed at https://code.google.com/p/chromium/issues/detail?id=391254

fixes CNVS-10808

test plan:
- using chrome
- Click the attach file icon
- Make sure the tooltip disappears

Change-Id: I86ff3bc9b2d309382c63b8fa4183bfc9b9162af6
Reviewed-on: https://gerrit.instructure.com/37255
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Colleen Palmer <colleen@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
Product-Review: Brad Horrocks <bhorrocks@instructure.com>