[STREAMING] [TEST] [HOTFIX] Fixed Kinesis test to not throw weird errors when...

[STREAMING] [TEST] [HOTFIX] Fixed Kinesis test to not throw weird errors when Kinesis tests are enabled without AWS keys

If Kinesis tests are enabled by env ENABLE_KINESIS_TESTS = 1 but no AWS credentials are found, the desired behavior is the fail the test using with
```
Exception encountered when attempting to run a suite with class name: org.apache.spark.streaming.kinesis.KinesisBackedBlockRDDSuite *** ABORTED *** (3 seconds, 5 milliseconds)
[info]   java.lang.Exception: Kinesis tests enabled, but could get not AWS credentials
```

Instead KinesisStreamSuite fails with

```
[info] - basic operation *** FAILED *** (3 seconds, 35 milliseconds)
[info]   java.lang.IllegalArgumentException: requirement failed: Stream not yet created, call createStream() to create one
[info]   at scala.Predef$.require(Predef.scala:233)
[info]   at org.apache.spark.streaming.kinesis.KinesisTestUtils.streamName(KinesisTestUtils.scala:77)
[info]   at org.apache.spark.streaming.kinesis.KinesisTestUtils$$anonfun$deleteStream$1.apply(KinesisTestUtils.scala:150)
[info]   at org.apache.spark.streaming.kinesis.KinesisTestUtils$$anonfun$deleteStream$1.apply(KinesisTestUtils.scala:150)
[info]   at org.apache.spark.Logging$class.logWarning(Logging.scala:71)
[info]   at org.apache.spark.streaming.kinesis.KinesisTestUtils.logWarning(KinesisTestUtils.scala:39)
[info]   at org.apache.spark.streaming.kinesis.KinesisTestUtils.deleteStream(KinesisTestUtils.scala:150)
[info]   at org.apache.spark.streaming.kinesis.KinesisStreamSuite$$anonfun$3.apply$mcV$sp(KinesisStreamSuite.scala:111)
[info]   at org.apache.spark.streaming.kinesis.KinesisStreamSuite$$anonfun$3.apply(KinesisStreamSuite.scala:86)
[info]   at org.apache.spark.streaming.kinesis.KinesisStreamSuite$$anonfun$3.apply(KinesisStreamSuite.scala:86)
```
This is because attempting to delete a non-existent Kinesis stream throws uncaught exception. This PR fixes it.

Author: Tathagata Das <tathagata.das1565@gmail.com>

Closes #7809 from tdas/kinesis-test-hotfix and squashes the following commits:

7c372e6 [Tathagata Das] Fixed test