lock test: make more robust against timing

Remove the stdout printing from the lock_test_help.py, so that there is no
problem with a failing test because one output ending up in stdout before the
other. So only output the current lock from lock_test.sh.

Change-Id: I7fe80a9de88ddee1d66ca5c692948fc9673e4230

selftest/lock_test.ok

@@ -1,8 +1,4 @@
-acquired lock: 'long name'
 launched first, locked by: long name
 launched second, locked by: long name
-leaving lock: 'long name'
-acquired lock: 'shorter'
 waited, locked by: shorter
-leaving lock: 'shorter'
 waited more, locked by: 

selftest/lock_test_help.py

@@ -14,12 +14,8 @@ lockfile_path = os.path.join(testdir, 'lock_test')
 fl = FileLock(lockfile_path, name)
 
 with fl:
-    print('acquired lock: %r' % fl.owner)
-    sys.stdout.flush()
     while os.path.exists(stop_signalling_file):
         time.sleep(.1)
-    print('leaving lock: %r' % fl.owner)
-    sys.stdout.flush()
 touch_file(stop_signalling_file + '.done')
 
 # vim: expandtab tabstop=4 shiftwidth=4