[test] Make test logging verbosity configurable with EV

Use the VERBOSE_TEST_LOGGING environment variable to
enable verbose logging for tests.

beat/core/test/__init__.py

@@ -57,7 +57,9 @@ network_name = os.environ.get('DOCKER_TEST_NETWORK', 'beat_core_test_network')
 network = None
 
 # Setup the logging system
-if False:
+VERBOSE_TEST_LOGGING = os.environ.get('VERBOSE_TEST_LOGGING', False) == 'True'
+
+if VERBOSE_TEST_LOGGING:
     formatter = logging.Formatter(fmt="[%(asctime)s - TESTS - "
                                       "%(name)s] %(levelname)s: %(message)s",
                                   datefmt="%d/%b/%Y %H:%M:%S")