remove instantiate_vapp_template helper dependencies
require vdc_id as a instantiate_vapp_template param
remove unnecessary helper
- make tags model to use post_undeploy_vapp
- fix syntax error in post_undeploy_vapp method
- remove post_vm_metadata
fix invalid syntax
fix situation where the content of the param can be false and not set the attr
Merge pull request #2259 from restebanez/vcloud_director/fix_instantiation_and_tags

Vcloud director/fix instantiation and tags creation