[SEBA-359]

Use 'levelname' key for field containg textual log level, to match
convention used in Python and Java code.

Change-Id: I62d8c8f8142451ac884dd2e867d1b14e5cfca268
diff --git a/common/logger/logger.go b/common/logger/logger.go
index 5830e3b..bd17385 100644
--- a/common/logger/logger.go
+++ b/common/logger/logger.go
@@ -44,7 +44,7 @@
 			&log.JSONFormatter{
 				FieldMap: log.FieldMap{
 					log.FieldKeyTime:  "@timestamp",
-					log.FieldKeyLevel: "level",
+					log.FieldKeyLevel: "levelname",
 					log.FieldKeyMsg:   "message",
 				},
 			},