Let oslotest manage the six.move setting for mox

This instruction to set up a move in six for the mox module conflicts
with the one in oslotest. We are trying to use mox3 everywhere, so
remove this instruction and let oslotest handle it.

Imported from the incubator change with the same ID.

Change-Id: I59d5799283233f8411044ddb15c8abfc8850014c