[FAB-3145] Override log level for ledger at peer start

This CR overrides the log level for all modules with ledger in their
module name during peer start. The value can be set in core.yaml using
`logging.ledger` or by using the CORE_LOGGING_LEDGER environment
variable.

Change-Id: Ia869573d7bb13a93468b70e5480e996b351775cb
Signed-off-by: Will Lahti <wtlahti@us.ibm.com>

Author: wlahti

peer/node/start.go

@@ -264,9 +264,9 @@ func serve(args []string) error {
 	logger.Infof("Started peer with ID=[%s], network ID=[%s], address=[%s]",
 		peerEndpoint.Id, viper.GetString("peer.networkId"), peerEndpoint.Address)
 
-	// set the logging level for specific modules defined in core.yaml.
-	// TODO Add calls to set 'ledger' module loggers
-	overrideLogModules := []string{"msp", "gossip"}
+	// set the logging level for specific modules defined via environment
+	// variables or core.yaml
+	overrideLogModules := []string{"msp", "gossip", "ledger"}
 	for _, module := range overrideLogModules {
 		err = common.SetLogLevelFromViper(module)
 		if err != nil {