Option to set Redis Leaf=False

Hello,

Just to mention that in some cases, Redis can be used as Lock mechanism. (ie https://pypi.org/project/python-redis-lock/).
In that case the code to monitor would look like follow :

```py
from redis_lock import Lock

with Lock("some key") :
#do something
```

In that case, you don't want Redis to be treated as a Leaf, so the rest can be tracked
Right now, all I have is a big redis span for the entire with.

I don't know what would be the best approach for this. perhaps having a class to handle BLPOP ?
https://github.com/ionelmc/python-redis-lock/blob/master/src/redis_lock/__init__.py#L249
https://github.com/redis/redis-py/blob/a87a750ed1a39138ba4526537335012fc95142c9/redis/commands/core.py#L1867

Thx