database/sql: fix some test fmt verbs

Found by vet.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/14762044

src/pkg/database/sql/convert_test.go

@@ -267,14 +267,14 @@ func TestValueConverters(t *testing.T) {
 			goterr = err.Error()
 		}
 		if goterr != tt.err {
-			t.Errorf("test %d: %s(%T(%v)) error = %q; want error = %q",
+			t.Errorf("test %d: %T(%T(%v)) error = %q; want error = %q",
 				i, tt.c, tt.in, tt.in, goterr, tt.err)
 		}
 		if tt.err != "" {
 			continue
 		}
 		if !reflect.DeepEqual(out, tt.out) {
-			t.Errorf("test %d: %s(%T(%v)) = %v (%T); want %v (%T)",
+			t.Errorf("test %d: %T(%T(%v)) = %v (%T); want %v (%T)",
 				i, tt.c, tt.in, tt.in, out, out, tt.out, tt.out)
 		}
 	}

src/pkg/database/sql/driver/types_test.go

@@ -51,14 +51,14 @@ func TestValueConverters(t *testing.T) {
 			goterr = err.Error()
 		}
 		if goterr != tt.err {
-			t.Errorf("test %d: %s(%T(%v)) error = %q; want error = %q",
+			t.Errorf("test %d: %T(%T(%v)) error = %q; want error = %q",
 				i, tt.c, tt.in, tt.in, goterr, tt.err)
 		}
 		if tt.err != "" {
 			continue
 		}
 		if !reflect.DeepEqual(out, tt.out) {
-			t.Errorf("test %d: %s(%T(%v)) = %v (%T); want %v (%T)",
+			t.Errorf("test %d: %T(%T(%v)) = %v (%T); want %v (%T)",
 				i, tt.c, tt.in, tt.in, out, out, tt.out, tt.out)
 		}
 	}