[Telemetry] Disable spaceport and tough_canvas_cases on mac.

They are timing out.

TBR=tonyg@chromium.org
NOTRY=True
BUG=

Review URL: https://codereview.chromium.org/100653004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238299 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238299