runner/executor: Inform about terminating

Create a message before terminating a running test and
inform user what is a cause.

Signed-off-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
Reviewed-by: Jan Sokolowski <jan.sokolowski@intel.com>
Reviewed-by: Ryszard Knop <rk@dragonic.eu>