load vcr in test mode

I use binstubs for my bundler. This fixes the following error:

```
$ ./bin/rspec spec/models/tag_spec.rb 
/Users/kbrock/src/manageiq/vmdb/spec/spec_helper.rb:89:in `<top (required)>': uninitialized constant VCR (NameError)
```

This does not install any different gems and does not affect the appliance since it is in the non appliance/test block

/cc @jrafanie