Alternate method to find compute resource to include cluster computer resources

find_compute_resource only finds VIM::ComputeResource
unrolled find_compute_resource to allow for ComputeResource or ClusterComputeResource
RbVmomi parser error with ClusterComputeResource, workaround handling exception and using alternate method to find childEntity in the folder.
Thanks @mkuzmin, I didn't notice in the gemspec a different maintainer, updating version to 1.8.2 shows followed the same process and that at least for me an exception is still raised.

Which RbVmomi should I be raising this against?

```
 INFO warden: Calling IN action: #<VagrantPlugins::VSphere::Action::Clone:0x54e7918>
C:/HashiCorp/Vagrant/embedded/lib/ruby/gems/2.0.0/gems/rbvmomi-1.8.2/lib/rbvmomi/connection.rb:61:in `parse_response'
C:/HashiCorp/Vagrant/embedded/lib/ruby/gems/2.0.0/gems/rbvmomi-1.8.2/lib/rbvmomi/connection.rb:90:in `call'
C:/HashiCorp/Vagrant/embedded/lib/ruby/gems/2.0.0/gems/rbvmomi-1.8.2/lib/rbvmomi/basic_types.rb:205:in `_call'
C:/HashiCorp/Vagrant/embedded/lib/ruby/gems/2.0.0/gems/rbvmomi-1.8.2/lib/rbvmomi/basic_types.rb:74:in `block (2 levels)
in init'
C:/HashiCorp/Vagrant/embedded/lib/ruby/gems/2.0.0/gems/rbvmomi-1.8.2/lib/rbvmomi/vim/Folder.rb:7:in `find'
C:/Data/Projects/GithubOS/vagrant-vsphere/lib/vSphere/util/vim_helpers.rb:46:in `find_clustercompute_or_compute_resource`
```