Avoid use of Objects.hash when there's only 1 params

- directly call #hashCode() when hashed Object seems non-null
- replace with Objects.hashCode(Object) when Nullable
- replace with Long.hashCode(long), etc. when primitive

Change-Id: I08c24ebbe94cf4162d1491209a14baf953163e41
diff --git a/ovsdb/rfc/src/main/java/org/onosproject/ovsdb/rfc/notation/OvsdbMap.java b/ovsdb/rfc/src/main/java/org/onosproject/ovsdb/rfc/notation/OvsdbMap.java
index fce3f69..a62ab0d 100644
--- a/ovsdb/rfc/src/main/java/org/onosproject/ovsdb/rfc/notation/OvsdbMap.java
+++ b/ovsdb/rfc/src/main/java/org/onosproject/ovsdb/rfc/notation/OvsdbMap.java
@@ -61,7 +61,7 @@
 
     @Override
     public int hashCode() {
-        return Objects.hash(map);
+        return map.hashCode();
     }
 
     @Override