Introduce tests.util module
    
    All the helper functions and constants moved to new util module.
    
    This module provides:
    
    - util.start_daemon() - starts a sanlock daemon process.
    
    - util.wait_for_daemon() - wait until sanlock daemon is ready.
    
    - util.sanlock() - run sanlock and return the output. Useful for running
      "sanlock client ..." or "sanlock direct ..." commands.
    
    - util.wait_for_termination - wait until a process terminates within a
      timeout.
    
    Signed-off-by: Nir Soffer <nsoffer@redhat.com>