Improve integration tests to test push scheduler mode as well

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**

At the moment, integration tests, setup cluster in `pull mode`

- https://github.com/apache/datafusion-ballista/blob/0396c58aa58a546395fa59bf6658e17c621c0cc3/ballista/client/tests/common/mod.rs#L104

as we make `push` scheduling default in https://github.com/apache/datafusion-ballista/pull/1461 we need to improve test to cover `push` scheduling.

**Describe the solution you'd like**

create new test setup which would start cluster using `push` scheduling and include it in the tests, preferably adding additional case to each test

**Describe alternatives you've considered**

**Additional context**

Start with ballista/client/tests/common/mod.rs around the cluster setup at the referenced line, then inspect the existing integration tests that use it. Add a push-scheduling cluster setup and include push-mode cases alongside the current pull-mode coverage. Done means the integration test suite exercises both scheduler modes successfully.

Written by the indexing model from the issue text.