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/core/api/src/main/java/org/onosproject/net/flow/instructions/L1ModificationInstruction.java b/core/api/src/main/java/org/onosproject/net/flow/instructions/L1ModificationInstruction.java
index c6847d1..b72dd7b 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/instructions/L1ModificationInstruction.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/instructions/L1ModificationInstruction.java
@@ -62,7 +62,7 @@
 
         @Override
         public int hashCode() {
-            return Objects.hash(oduSignalId);
+            return oduSignalId.hashCode();
         }
 
         @Override