Fix go-logging concurrent map read-write bug

This bug sometimes fails unit tests because logging are sometimes set up
in parallel.

Added a RWLock to op/go-logging/level.go's moduleLeveled struct
and it RLocks in GetLevel and WLocks at SetLevel

Change-Id: I78e837879fece869af9a5e573930492d439a6e82
Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>

core/util/utils_test.go

@@ -21,6 +21,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/op/go-logging"
 )
 
 func TestComputeCryptoHash(t *testing.T) {
@@ -98,3 +100,21 @@ func TestFindMissingElements(t *testing.T) {
 		}
 	}
 }
+
+// This test checks go-logging is thread safe with regard to
+// concurrent SetLevel invocation and log invocations.
+// Fails without the concurrency fix (adding RWLock to level.go)
+// In case the go-logging will be overwritten and its concurrency fix
+// will be regressed, this test should fail.
+func TestConcurrencyNotFail(t *testing.T) {
+	logger := logging.MustGetLogger("test")
+	go func() {
+		for i := 0; i < 100; i++ {
+			logging.SetLevel(logging.Level(logging.DEBUG), "test")
+		}
+	}()
+
+	for i := 0; i < 100; i++ {
+		logger.Info("")
+	}
+}