all: fix go vet warnings

trie/proof_test.go

@@ -124,7 +124,7 @@ func BenchmarkVerifyProof(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		im := i % len(keys)
 		if _, err := VerifyProof(root, []byte(keys[im]), proofs[im]); err != nil {
-			b.Fatalf("key %x: error", keys[im], err)
+			b.Fatalf("key %x: %v", keys[im], err)
 		}
 	}
 }

trie/trie_test.go

@@ -65,7 +65,7 @@ func TestMissingRoot(t *testing.T) {
 		t.Error("New returned non-nil trie for invalid root")
 	}
 	if _, ok := err.(*MissingNodeError); !ok {
-		t.Error("New returned wrong error: %v", err)
+		t.Errorf("New returned wrong error: %v", err)
 	}
 }