Flaky CQL test: AbstractIndexManagementIT.testRepairRelationIndex

## Flaky Test

* **Test Name:** CQLIndexManagementIT>AbstractIndexManagementIT.testRepairRelationIndex
* **Link:** https://github.com/JanusGraph/janusgraph/blob/ffc19fc18d56f027935d57dc69c99cf68c01f662/janusgraph-hadoop/src/test/java/org/janusgraph/hadoop/AbstractIndexManagementIT.java#L176
* **Branch:** `master` (the PR was #3130)
* **Notes:**

### Stack Trace

The summary was:
```
Error: Failures:
Error: CQLIndexManagementIT>AbstractIndexManagementIT.testRepairRelationIndex:192 expected: but was:
```

Not sure if the included stack trace is relevant, so I'm just pasting everything from the log related to this test run:

```
[INFO] -------------------------------------------------------
[INFO] T E S T S
[INFO] -------------------------------------------------------
[INFO] Running org.janusgraph.hadoop.CQLIndexManagementIT
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/runner/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.17.1/log4j-slf4j-impl-2.17.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/runner/.m2/repository/ch/qos/logback/logback-classic/1.2.7/logback-classic-1.2.7.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
log4j:WARN No appenders could be found for logger (org.apache.htrace.core.Tracer).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Error: Tests run: 5, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 204.245 s <<< FAILURE! - in org.janusgraph.hadoop.CQLIndexManagementIT
Error: testRepairRelationIndex Time elapsed: 67.658 s <<< FAILURE!
org.opentest4j.AssertionFailedError: expected: but was:
[INFO] Running org.janusgraph.hadoop.CQLInputFormatIT
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/runner/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.17.1/log4j-slf4j-impl-2.17.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/runner/.m2/repository/ch/qos/logback/logback-classic/1.2.7/logback-classic-1.2.7.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
log4j:WARN No appenders could be found for logger (org.apache.htrace.core.Tracer).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
java.util.concurrent.RejectedExecutionException: Task scala.concurrent.impl.CallbackRunnable@ae87d5a rejected from java.util.concurrent.ThreadPoolExecutor@42f8277[Shutting down, pool size = 3, active threads = 1, queued tasks = 0, completed tasks = 2]
at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2063)
at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:830)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1379)
at scala.concurrent.impl.ExecutionContextImpl$$anon$4.execute(ExecutionContextImpl.scala:138)
at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:72)
at scala.concurrent.impl.Promise$DefaultPromise.$anonfun$tryComplete$1(Promise.scala:288)
at scala.concurrent.impl.Promise$DefaultPromise.$anonfun$tryComplete$1$adapted(Promise.scala:288)
at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:288)
at scala.concurrent.Promise.complete(Promise.scala:53)
at scala.concurrent.Promise.complete$(Promise.scala:52)
at scala.concurrent.impl.Promise$DefaultPromise.complete(Promise.scala:187)
at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:33)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:750)
java.util.concurrent.RejectedExecutionException: Task scala.concurrent.impl.CallbackRunnable@58ffd281 rejected from java.util.concurrent.ThreadPoolExecutor@563837ee[Shutting down, pool size = 1, active threads = 1, queued tasks = 0, completed tasks = 2]
at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2063)
at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:830)
at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1379)
at scala.concurrent.impl.ExecutionContextImpl$$anon$4.execute(ExecutionContextImpl.scala:138)
at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:72)
at scala.concurrent.impl.Promise$DefaultPromise.$anonfun$tryComplete$1(Promise.scala:288)
at scala.concurrent.impl.Promise$DefaultPromise.$anonfun$tryComplete$1$adapted(Promise.scala:288)
at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:288)
at scala.concurrent.Promise.complete(Promise.scala:53)
at scala.concurrent.Promise.complete$(Promise.scala:52)
at scala.concurrent.impl.Promise$DefaultPromise.complete(Promise.scala:187)
at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:33)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:750)
[INFO] Tests run: 11, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 173.844 s - in org.janusgraph.hadoop.CQLInputFormatIT
[INFO] Running org.janusgraph.hadoop.CQLScanJobIT
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/runner/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.17.1/log4j-slf4j-impl-2.17.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/runner/.m2/repository/ch/qos/logback/logback-classic/1.2.7/logback-classic-1.2.7.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
log4j:WARN No appenders could be found for logger (org.apache.htrace.core.Tracer).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
[INFO] Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 134.104 s - in org.janusgraph.hadoop.CQLScanJobIT
[INFO]
[INFO] Results:
[INFO]
Error: Failures:
Error: CQLIndexManagementIT>AbstractIndexManagementIT.testRepairRelationIndex:192 expected: but was:
[INFO]
Error: Tests run: 19, Failures: 1, Errors: 0, Skipped: 0
```

Start with janusgraph-hadoop/src/test/java/org/janusgraph/hadoop/AbstractIndexManagementIT.java around line 176 and the CQLIndexManagementIT.testRepairRelationIndex failure at line 192. Run the named integration test repeatedly and inspect the assertion and related log output. Done means the test no longer flakes and the CQL index-repair check passes reliably.

Written by the indexing model from the issue text.