initialize max_stream_priorities in getStreamFromPool(bool) (#102739)
Summary:
`getStreamFromPool(bool, signed char)` overload doesn't initialize `max_stream_priorities`. So if we call `getStreamFromPool(true)` we would hit the following error
```
terminate called after throwing an instance of 'c10::Error'
what(): Expected cuda stream priority to be less than or equal to 0, got 1
```
Differential Revision: D46358087
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102739
Approved by: https://github.com/ngimel
