Add missing query tests

In our Gremlin query test suites, we do not have tests that would test the following pattern of queries:

1. "....blah().barrier().as('x')....blah().select('x')"
2. "....blah().valueMap().as('x')....blah().select('x')"
3. "....blah().path().as('x')....blah().select('x')"
4. "....blah().count().as('x')....blah().select('x')"

The category of tests can be clubbed into defining an alias and using the value of the alias further ahead in the traversal.