Fix a memory leak in |NCONF_free|.

As I read it:

1. |_LHASH| contains
2.   buckets of |LHASH_ITEMS|, which contain
3.     |CONF_VALUE|s, which contain
4.       various bits of data.

The previous code was freeing #1 and #2 in |lh_free|, and #4 in
|value_free_contents|, but was failing to free the |CONF_VALUE|s
themselves.  The fix is to call |value_free| rather than
|value_free_contents|.

Change-Id: I1d5b48692ca9ac04df688e45d7fc113dc5cd6ddf
Reviewed-on: https://boringssl-review.googlesource.com/5742
Reviewed-by: Adam Langley <[email protected]>

crypto/conf/conf.c

@@ -137,7 +137,7 @@ void NCONF_free(CONF *conf) {
     return;
   }
 
-  lh_CONF_VALUE_doall(conf->data, value_free_contents);
+  lh_CONF_VALUE_doall(conf->data, value_free);
   lh_CONF_VALUE_free(conf->data);
   OPENSSL_free(conf);
 }