config: fix a conflicting test name

A public API TestNewRawConfig was added to easily create a raw config
for testing, but this conflicted with the test. Just rename it.

config/raw_config_test.go

@@ -27,7 +27,7 @@ func TestNewRawConfig(t *testing.T) {
 	}
 }
 
-func TestRawConfig(t *testing.T) {
+func TestRawConfig_basic(t *testing.T) {
 	raw := map[string]interface{}{
 		"foo": "${var.bar}",
 	}