command: Fix log message verification

The root cause of the change is a flaky behaviour of a couple of the tests in the command package. The tests assume the first log message would be the output of the bash script that is invoked. But it happens that 'spawn token acquired' text is the first message instead. It seems weird why it differs from time to time, but the solution is pretty strait forward: search for th message we are interested in. All others will be skipped.

Closes: #3980 (closed)