Fix hphp/test/frameworks under the typechecker again

Reviewed By: @JoelMarcey

Differential Revision: D1403949
Add sequential + test find mode options to frameworks.yaml

Reviewed By: @JoelMarcey

Differential Revision: D1404194
Add isolation mode for OSS tests

Summary: An alternative approach to finding flakey tests. Finds a few issues, eg that assetic does shell_exec('php '..., so those tests aren't actually tested against the right build of HHVM.

Not on by default.

Reviewed By: @JoelMarcey

Differential Revision: D1403101