clean bundler env before calling out to bosh-registry

This was discovered to be necessary when using non-standard ruby/bundler locations and invoking `bosh micro deploy`.
What will go wrong outside of bundler?

On Tue, Dec 23, 2014 at 4:26 PM, Dmitriy Kalinin <notifications@github.com>
wrote:

>> @@ -30,7 +30,9 @@ def start
>>  
>>        cmd = "bosh-registry -c #{@registry_config.path}"
>>  
>> -      @registry_pid = Process.spawn(cmd)
>> +      Bundler.with_clean_env {
> I dont think we can do that because CLI plugin does not depend on bundler. Tests happen to pass because they run in `bundle exec`?
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/cloudfoundry/bosh/pull/720/files#r22241953