Locally disable rspec warning of message expectations on nil object

I disable the warning only in the context of a single example where
the test deliberately sets the user to nil and set message
expectations on it.

The warnings were:
```
      when current user is nil
An expectation of :present? was set on nil. Called from /home/david2/LocalSupport/spec/controllers/volunteer_ops_controller_spec.rb:121:in `block (5 levels) in <top (required)>'. Use allow_message_expectations_on_nil to disable warnings.
An expectation of :organization was set on nil. Called from /home/david2/LocalSupport/spec/controllers/volunteer_ops_controller_spec.rb:122:in `block (5 levels) in <top (required)>'. Use allow_message_expectations_on_nil to disable warnings.
```
Restore commit "vagrant file with some networking update"

This reverts commit 426c57755ba6eda81546604261a4d28cf967277c.

Original was commit 15d5749d6f1f9b678db8c7aefc4a7acc8fd88af4
Author: Sam Joseph <tansaku@gmail.com>
Date:   Fri Jun 6 20:57:32 2014 +0100

It allows a Vagrant VirtualBox host machine to move from
one network to another without restarting the Local Support guest.

http://stackoverflow.com/questions/18457306/enable-internet-access-inside-vagrant
Integrate Vagrantfile changes into upstream
Describe rake db:import:emails[file]

so that it is listed by `rake -T`
Merge pull request #53 from dcorking/vagrant-networking-tweaks

Vagrant networking tweaks for Sam
Merge pull request #52 from dcorking/fix-rspec-nil-warning

Disable rspec nil warning
Merge pull request #55 from dcorking/desc-emails-rake

Describe emails rake task
adds id attrib to button-rack, balances top/bottom padding
Merge pull request #45 from johnnymo87/button-rack

top/bottom padding changes wasn't being applied, switched to using id
revises feature description
some basic improvements to volunteer page
Merge pull request #56 from tansaku/volunteer_show_page

some basic improvements to volunteer page
[WIP] failing test for hyperlinking organization
now failing for the right reason
WIP: spec for vol op show page link failing
added organisation hyperlink
Merge branch 'develop' of https://github.com/AgileVentures/LocalSupport into develop