[API] Syncing of the tags between AKSConfig and UpstreamSpec for a newly created cluster is slow for empty tags

[valaparthvi]

Create a cluster with a few tags and an empty tag, for e.g: {"owner": "pvala", "testLine": "somefile_L45", "empty-tag": ""}

When the cluster is created, Azure portal adds its own set of tags and the syncing between AKSConfig tags and UpstreamSpec tags is not immediate, it takes a few minutes after the cluster is Active before everything is synced.

I noticed that the non-empty tags immediately appear on AKS console, but the empty tag takes a while to appear, so there is something amiss with the way operator deals with empty tags.
IMO the sync should complete before the cluster becomes active.

This happens for both API and UI cluster creation. Updating the cluster with an empty tag via API works as expected.