These tests use devicestorage_setup() in devicestorage_common() to do
two things:
a) Set up preferences using pushPrefEnv().
b) Delete a special directory for testing device storage things, to
make sure it is empty. This requires running a chrome script and
waiting for it to finish.
Actually converting the individual tests requires wrapping up the
rest of the test inside a giant function.
This patch also removes the non-e10s ipc tests, because the other
changes break them. They should not be needed any more, as with this
patch we will be running devicestorage tests on e10s and b2g.