[SPARK-14713][TESTS] Fix the flaky test NettyBlockTransferServiceSuite

## What changes were proposed in this pull request?

When there are multiple tests running, "NettyBlockTransferServiceSuite.can bind to a specific port twice and the second increments" may fail.

E.g., assume there are 2 tests running. Here are the execution order to reproduce the test failure.

| Execution Order | Test 1 | Test 2 |
| ------------- | ------------- | ------------- |
| 1 | service0 binds to 17634 |  |
| 2 |  | service0 binds to 17635 (17634 is occupied) |
| 3 | service1 binds to 17636 |  |
| 4 | pass test |  |
| 5 | service0.close (release 17634) |  |
| 6 |  | service1 binds to 17634 |
| 7 |  | `service1.port should be (service0.port + 1)` fails (17634 != 17635 + 1) |

Here is an example in Jenkins: https://amplab.cs.berkeley.edu/jenkins/view/Spark%20QA%20Test/job/spark-master-test-maven-hadoop-2.2/786/testReport/junit/org.apache.spark.network.netty/NettyBlockTransferServiceSuite/can_bind_to_a_specific_port_twice_and_the_second_increments/

This PR makes two changes:

- Use a random port between 17634 and 27634 to reduce the possibility of port conflicts.
- Make `service1` use `service0.port` to bind to avoid the above race condition.

## How was this patch tested?

Jenkins unit tests.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #12477 from zsxwing/SPARK-14713.

0 files changed, 0 insertions, 0 deletions