Optimize the peeking on newly acquired connection on *unix. Use syscall
to peek on the socket instead of blocking for a fixed amount of time.
This won't work on Windows, hence the `MaybeHasData` will always return
true on Windows and the client will have to block for a given time to
actually peek on the socket.
*Time to complete N HSET operations (individual commands)*
| Batch Size | Before (total sec) | After (total sec) | Time Saved | % Faster |
|------------|-------------------|------------------|------------|----------|
| 100 ops | 0.0172 | 0.0133 | 0.0038 | **22.4%** |
| 1K ops | 0.178 | 0.133 | 0.045 | **25.3%** |
| 10K ops | 1.72 | 1.28 | 0.44 | **25.6%** |
| 100K ops | 17.1 | 13.4 | 3.7 | **22.0%** |
