Remove metadata overhead warning for full ejection buckets

We have a metadata overhead warning that appears if the metadata in memory uses over 50%:

Metadata overhead warning. Over  XX% of RAM allocated to bucket  "YY" on node "ZZ" is taken up by keys and metadata.

In the context of a full eviction bucket it doesn't make a lot of sense to show these warnings since the user doesn't really need to act on them (whereas they might in value eviction).

The net effect of this is that the user gets unnecessarily concerned and the logs get spammed with the same message over and over again.