BUG-1381: guide users to use external synchronized block

This will prevent potential misuses and allow us to scale the utility
class further.

Change-Id: I14bbbf76ccfc7e0ff7942880b25d1f6d5964283e
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-1381: guide users to use external synchronized block"