Tag mechanism supports network, subnet, port, subnetpool
router resources only. This patch allow tag mechanism to support
resources with standard attribute.
Two old extenions are kept because of backward compatibility.
They will be removed in Queens release.
APIImpact: Tag is supported by resources with standard attribute
DocImpact: allow users to set tags on resources with standard attribute
Change-Id: Id7bb13b5beb58c313eea94ca03835d3daf5c94bc
Closes-Bug: #1682775
