`rsvpErrorHandler` always throws async.
Add IE9 to sauce tests.

Removed flaky check for `sandbox` which is already not required anyway as we
support IE8 and IE9, albeit using cross-origin and with the associated caveats.
Oasis' bootloader can be hosted on a separate domain.

This is workaround, we plan on implementing a handshake
to confirm when the iframe/web worker is loaded.