Fixes #4450, add another expand_path ../ to get back to the guests directory

When installing from master after #4438 fix was in, I get the following error, which this PR fixes:

    vagrant up test7
    Bringing machine 'test7' up with 'virtualbox' provider...
    ==> test7: Importing base box 'opscode-centos-7.0'...
    ==> test7: Matching MAC address for NAT networking...
    ==> test7: Setting the name of the VM: test7
    ==> test7: Clearing any previously set network interfaces...
    ==> test7: Preparing network interfaces based on configuration...
        test7: Adapter 1: nat
        test7: Adapter 2: hostonly
    ==> test7: Forwarding ports...
        test7: 22 => 2222 (adapter 1)
    ==> test7: Running 'pre-boot' VM customizations...
    ==> test7: Booting VM...
    ==> test7: Waiting for machine to boot. This may take a few minutes...
        test7: SSH address: 127.0.0.1:2222
        test7: SSH username: vagrant
        test7: SSH auth method: private key
        test7: Warning: Connection timeout. Retrying...
    ==> test7: Machine booted and ready!
    ==> test7: Checking for guest additions in VM...
    ==> test7: Setting hostname...
    ==> test7: Configuring and enabling network interfaces...
    ==> test7: Forcing shutdown of VM...
    ==> test7: Destroying VM and associated drives...
    /path/to/gems/vagrant-1.6.4/plugins/guests/redhat/cap/configure_networks.rb:26:in `require': cannot load such file -- /path/to/gems/vagrant-1.6.4/plugins/guests/redhat/fedora/cap/configure_networks (LoadError)
      from /path/to/gems/vagrant-1.6.4/plugins/guests/redhat/cap/configure_networks.rb:26:in `configure_networks_rhel7'
      from /path/to/gems/vagrant-1.6.4/plugins/guests/redhat/cap/configure_networks.rb:17:in `configure_networks'