Branching tests do not produce good hashgraphs

Our current tests for branching do not limit the number of nodes that branch to <1/3 of the total consensus weight. This violates a fundamental requirement that fewer than 1/3 of nodes are dishonest, and is therefore an invalid test scenario.

Start by locating the current branching tests in the Java consensus code and review how they choose the nodes that branch. Confirm the test scenario against the total consensus weight and the fewer-than-one-third dishonest-node requirement. Done means the branching tests no longer construct scenarios that violate this requirement.

Written by the indexing model from the issue text.