Use non-Admin API to query VMs wherever possible

[andrew-lee-1089]

If possible do not use the Admin API:

In the query_vm_by_name method use the non-Admin API
I was tempted just to create a new method called query_vm_by_name_not_as_admin but decided that wasn't necessary: I think this fine, both the Admin and non-Admin query return an XML object with a 'href' which is what we care about:
As per https://www.vmware.com/support/vcd/doc/rest-api-doc-1.5-html/types/QueryResultVMRecordType.html and https://www.vmware.com/support/vcd/doc/rest-api-doc-1.5-html/types/QueryResultAdminVMRecordType.html both return something with a href

@shashim22 added this method last summer in https://github.com/vmware/pyvcloud/pull/367/files so should definitely review, :-)

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