Update Vagrantfile to only sync raw bosh repository.
Remove AWS network stage

We should consider the network initialization an agent behavior instead
of a stemcell responsibility because:

- The setup we had in the stage is highly Debian specific
- The work is done by the agent already
- The agent has proper OS depdent behavior for initial network setup

Signed-off-by: caleb miles <cmiles@pivotallabs.com>