[FLAKY-TEST] InputStreamsSuite.socket input stream

## What changes were proposed in this pull request?

https://spark-tests.appspot.com/test-details?suite_name=org.apache.spark.streaming.InputStreamsSuite&test_name=socket+input+stream

## How was this patch tested?

Tested 2,000 times.

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #16343 from brkyvz/sock.