wash validate should ensure that every node in an entry's schema's been validated

[ekinanp]

Given something like

bolt
└── [group]
    └── [target]
        └── fs

wash validate should ensure that at least one instance of bolt, group, target, and fs have been validated (but only if an entry's schema has been provided). The current code doesn't do that because it randomly selects the child it will recurse into. So, if it happens to select a group instance that has no children, then wash validate will fail to validate a target and fs instance.