Inconsistent AWS environment variables in documentation

Looking at the actual Scala code, the environment variables used to log into AWS are:

• AWS_ACCESS_KEY_ID
• AWS_SECRET_ACCESS_KEY
• AWS_SESSION_TOKEN

These are the same that AWS uses in their libraries.

However, looking through the Spark documentation and comments, I see that these are not denoted correctly across the board:

docs/cloud-integration.md
106:1. `spark-submit` reads the `AWS_ACCESS_KEY`, `AWS_SECRET_KEY` <-- both different
107:and `AWS_SESSION_TOKEN` environment variables and sets the associated authentication options

docs/streaming-kinesis-integration.md
232:- Set up the environment variables `AWS_ACCESS_KEY_ID` and `AWS_SECRET_KEY` with your AWS credentials. <-- secret key different

external/kinesis-asl/src/main/python/examples/streaming/kinesis_wordcount_asl.py
34: $ export AWS_ACCESS_KEY_ID=<your-access-key>
35: $ export AWS_SECRET_KEY=<your-secret-key> <-- different
48: Environment Variables - AWS_ACCESS_KEY_ID and AWS_SECRET_KEY <-- secret key different

core/src/main/scala/org/apache/spark/deploy/SparkHadoopUtil.scala
438: val keyId = System.getenv("AWS_ACCESS_KEY_ID")
439: val accessKey = System.getenv("AWS_SECRET_ACCESS_KEY")
448: val sessionToken = System.getenv("AWS_SESSION_TOKEN")

external/kinesis-asl/src/main/scala/org/apache/spark/examples/streaming/KinesisWordCountASL.scala
53: * $ export AWS_ACCESS_KEY_ID=<your-access-key>
54: * $ export AWS_SECRET_KEY=<your-secret-key> <-- different
65: * Environment Variables - AWS_ACCESS_KEY_ID and AWS_SECRET_KEY <-- secret key different

external/kinesis-asl/src/main/java/org/apache/spark/examples/streaming/JavaKinesisWordCountASL.java
59: * $ export AWS_ACCESS_KEY_ID=[your-access-key]
60: * $ export AWS_SECRET_KEY=<your-secret-key> <-- different
71: * Environment Variables - AWS_ACCESS_KEY_ID and AWS_SECRET_KEY <-- secret key different