[V3 JSON] Drivers deepcopy input/output data (#1855)

* [V3 JSON] Return deepcopy in JSON driver

* Add a test

* foo not bar

* Add a test for setting and then mutating

* Resolve issue for setting and mutating as well

* Reformat

redbot/core/config.py

@@ -335,7 +335,7 @@ class Group(Value):
                 default = poss_default
 
         try:
-            return deepcopy(await self.driver.get(*self.identifiers, *path))
+            return await self.driver.get(*self.identifiers, *path)
         except KeyError:
             if default is not ...:
                 return default
@@ -365,7 +365,7 @@ class Group(Value):
 
         """
         if not defaults:
-            defaults = deepcopy(self.defaults)
+            defaults = self.defaults
 
         for key, value in current.items():
             if isinstance(value, collections.Mapping):