Travis 14.04 support: Don't run `stbt camera` tests
Travis 14.04 support: Don't run `stbt camera` tests

...because they have frequent intermittent failures. The tests will be
worked on and re-enabled at a later date.

We don't run these tests at the moment on our existing Travis
infrastructure because Ubuntu 12.04 doesn't have the necessary GStreamer
elements. So this isn't a regression in test coverage.

LewisHaley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester