`berks vendor` "cannot be trusted!" error

Since upgrading from `beta6` to `rc1` I'm getting the following error:


```
$ be berks vendor /Users/Jean/code/kabisa/internal/server-provisioning/tmp/tests \
    --berksfile /Users/Jean/code/kabisa/internal/server-provisioning/cookbooks/wrappers/base/Berksfile \
    -d
```

```
# ...

I, [2014-04-11T14:02:03.404224 #91543]  INFO -- : Checking if lockfile is trusted
D, [2014-04-11T14:02:03.404256 #91543] DEBUG -- : Checking base (1.5.2)
D, [2014-04-11T14:02:03.404276 #91543] DEBUG -- :   Detected there is a cached cookbook
D, [2014-04-11T14:02:03.404337 #91543] DEBUG -- :   Different location - cannot be trusted!
D, [2014-04-11T14:02:03.404511 #91543] DEBUG -- :     Dependency location: #<Berkshelf::PathLocation metadata: true, path: .>
D, [2014-04-11T14:02:03.404718 #91543] DEBUG -- :     Locked location:     #<Berkshelf::PathLocation metadata: false, path: ../../..>
I, [2014-04-11T14:02:03.404745 #91543]  INFO -- : Installing from universe
Fetching 'base' from source at ../../..
The resource at '/Users/Jean/code/kabisa/internal/server-provisioning' does not appear to be a valid cookbook. Does it have a metadata.rb?
	/Users/Jean/.gem/ruby/2.1.0/gems/berkshelf-3.0.0.rc1/lib/berkshelf/locations/base.rb:59:in `validate_cached!'
	/Users/Jean/.gem/ruby/2.1.0/gems/berkshelf-3.0.0.rc1/lib/berkshelf/locations/path.rb:16:in `install'
```

Not sure how, but the path in the `Locked location` seems to be the issue.