Information about warmup misleading

The note about not all the keys and data having to be loaded in order for the server to serve data during warmup is misleading. While the note is true for full eviction it is misleading for value eviction as all keys must be loaded before data can be served.

Overall the note should probably say something more along the lines of:

Couchbase Server is capable of serving data before it actually loads all the keys and data from the vBuckets.
However, in value eviction mode, all keys must be loaded from disk before data can be served.