Major Description
The behaviour of MetadataStore.getRangeKVs is changed with HDFS-12572. An empty list will be returned instead of an IOException in case of non existing key.
But at a few places the javadoc has not been updated.
This patch fixes the javadoc according to the improved implementation and add an additional test to prove the defined behaviour. (And fixes a small typo in the javadoc of the unit test).