[FAB-6315] Submodule log level override at peer start

This CR enables overriding the default log level for a submodule
at peer start (e.g. peer/gossip). In order to set these variables
from both yaml files and environment variables, the submodule
name must be supplied using periods instead of the forward
slashes used in logging module names, hence the replacement of
periods with forward slashes.

Change-Id: I58234e6e81641709e84b8df28162539d53c7126f
Signed-off-by: Will Lahti <wtlahti@us.ibm.com>

peer/common/common.go

@@ -19,6 +19,7 @@ package common
 import (
 	"fmt"
 	"os"
+	"strings"
 
 	"github.com/hyperledger/fabric/bccsp/factory"
 	"github.com/hyperledger/fabric/common/channelconfig"
@@ -208,6 +209,9 @@ func SetLogLevelFromViper(module string) error {
 	if err != nil {
 		return err
 	}
+	// replace period in module name with forward slash to allow override
+	// of logging submodules
+	module = strings.Replace(module, ".", "/", -1)
 	// only set logging modules that begin with the supplied module name here
 	_, err = flogging.SetModuleLevel("^"+module, logLevelFromViper)
 	return err