MODE-1865 Test case to show non deterministic query results.
MODE-1865 Test case now fails much more likely (hopefully 100%).
MODE-1865 Fix for bug. Do not push down isExists query hint to join query contexts.
MODE-1865 Additional changes and fixes

The test case added in previous commits (for this issue) was not cleaning
up the 300 nodes it was creating and using for the queries, thus causing
failures in many subsequent tests. This was corrected, and the test case
simplified. The changes to QueryProcessor were also incomplete and did
not always return just one row when using "LIMIT 1", so this was corrected.
MODE-1878 Corrected determination of correct SNS child node definitions

When a node with a child is persisted, and then a new child node with the
same name as the existing child is added to the parent, and when the
parent node type contains more than one applicable residual child node definition,
ModeShape incorrected determined that no child node definition could be
found for the new SNS child.

Two new test cases were added to replicate this scenario, and the
validation logic was corrected.