Use paseos_instance.wait_for_activity() in tests

# Feature
## Desired Behavior / Functionality
The tests use a locally defined wait_for_activity function, we should use the new `paseos_instance.wait_for_activity()` function instead.

(introduced in #116)

## What Needs to Be Done

Go through tests and use `paseos_instance.wait_for_activity()` where appropriate

## How Can It Be Tested

Run tests.