Integration test framework prefers global binary over current built

[Licenser]

Problem

The integration tests pick up a global tremor if installed which makes them an extremely confusing experience when running them during development. Running cargo run ... does in fact run the integration test with not the newly built tremor but instead the existing old one a very unexpected behaviour.

Steps

1. Install tremor
2. do a code change
3. run cargo run -p tremor-cli -- test integration tremor-cli/tests to run the tests
4. The old binary is used

Possible Solution(s)

For spawning sub instances the integration test should always use its own binary.