Add slf4j-simple for tests
Add slf4j-simple for tests

Just to activate logging, so we get something, not the NOOP
implementation.

Change-Id: I0c485264bfef4ce9944c970cb453c9049fd44bee
Signed-off-by: Robert Varga <b8bd3df785fdc0ff42dd1710c5d91998513c57ef@cisco.com>

NovusTheory/yangtools,opendaylight/yangtools,opendaylight/yangtools,522986491/yangtools