Sampling: Copy over iterable overrides

If an override was iterable, any modifications to the returned value
would alter the reference to the global storage dict.

Therefore, copy the structure if it's an iterable so any modification
won't alter the original override. Also apply this for the function
that checks for forced overrides.

Signed-off-by: kingbri <bdashore3@proton.me>

common/utils.py

@@ -15,6 +15,6 @@ def coalesce(*args):
 
 
 def prune_dict(input_dict):
-    """Trim out instances of None from a dictionary"""
+    """Trim out instances of None from a dictionary."""
 
     return {k: v for k, v in input_dict.items() if v is not None}