Boot timeout issue

I was unable to boot into my ubuntu parallels images (13.10 amd64) with the 0.2.0 version of vagrant-parallels.  It would get stuck in the following place.

```
[default] Importing base box 'saucy-parallels'...
[default] Matching MAC address for Shared network...
[default] The specified base MAC is already in use. Generating a new unique MAC
address for Shared network...
[default] Preparing network interfaces based on configuration...
[default] Clearing any previously set network interfaces...
[default] Running 'pre-boot' VM customizations...
[default] Booting VM...
[default] Waiting for machine to boot. This may take a few minutes...
```

For me, it turned out to be an issue with the network interfaces, and the workaround would be to run `sudo dhclient eth0` which in turn would resume the boot process.  For me, removing the network_adapter(0, :shared) call in the initialize method of config.rb, solved this problem.

Using Parallels 9.0.24172 on OSX 10.8.5 with Vagrant 1.4.3.