only print hh.conf once, plus bugfix
Summary:
When we start up hack, the server log contains numerous copies of the config (hh.conf, plus overrides). This diff simplifies it. It no longer prints the baseline hh.conf. It instead prints each override once, and then prints the entire combined config once.
One change is that `Config_file.parse*` is now always silent.
Also, I think there was a bug before where "apply CLI overrides" was only used in some cases (namely, if there were experiments_config); it should really be applied in all cases. This diff fixes it.
Differential Revision:
D32930474
fbshipit-source-id:
2c431512366a98d940e82d19de96053588be7486