[EC2] [SPARK-6600] Open ports in ec2/spark_ec2.py to allow HDFS NFS gateway

[florianverhein]

Authorizes incoming access to master on the ports required to use the hadoop hdfs nfs gateway from outside the cluster.

[SparkQA]

Test build #29389 has started for PR 5257 at commit 72a586a.

[florianverhein]

Some things to think about:

• Do we want an option for this (e.g. as for ganglia)? I haven't done this as I think it would be confusing at the moment, since a user would assume that the option would enable the hdfs nfs gateway on the cluster. However as far as I'm aware, spark-ec2 doesn't do this yet ([SPARK-8060] Improve DataFrame Python test coverage and documentation. #6601). So I think it would be better if the option were added as part of that work.
• Further, since the ports are opened to the authorized address, I don't see a problem in having this done by default for now.

I have tested this with a spark-ec2 cluster running the gateway (i.e. with these settings, I can mount the hfds on my local machine - which is really handy!)

[SparkQA]

Test build #29389 has finished for PR 5257 at commit 72a586a.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.
• This patch does not change any dependencies.

[AmplabJenkins]

Test PASSed.
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https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/29389/
Test PASSed.

[srowen]

I think this seems reasonable. I'll leave it open for comments for some time.