tests: use tracker-control to terminate tracker

The while loop is necessary, as `tracker-control -t` works
asynchronously.

Relates NEMO#530
tests: do not use "su" to execute test steps

Relates NEMO#530
tests: fix paths to ut_* executables

Relates NEMO#530
tests: mcclient6-wait-for-name -> mc-wait-for-name

Relates NEMO#530