testing: setting env var incompatible with parallel tests (#14405)

Neither the `os.Setenv` nor `t.Setenv` helper are safe to use in parallel tests
because environment variables are process-global. The stdlib panics if you try
to do this. Remove the `ci.Parallel()` call from all tests where we're setting
environment variables.

api/api_test.go

@@ -117,7 +117,7 @@ func TestRequestTime(t *testing.T) {
 }
 
 func TestDefaultConfig_env(t *testing.T) {
-	testutil.Parallel(t)
+
 	testURL := "http://1.2.3.4:5678"
 	auth := []string{"nomaduser", "12345"}
 	region := "test"