fix(config): no legacy over non-legacy override (#2644)

Do not take legacy property into account if there's non-legacy value.

react/features/base/config/reducer.js

 
     /* eslint-enable indent */
 
-        if (oldKey in newValue) {
+        if (oldKey in newValue && !(newKey in newValue.p2p)) {
             const v = newValue[oldKey];
 
             // Do not modify oldValue.