[SPARK-3332] Revert spark-ec2 patch that identifies clusters using tags

[JoshRosen]

This reverts #1899 and #2163, two patches that modified spark-ec2 so that clusters are identified using tags instead of security groups. The original motivation for this patch was to allow multiple clusters to run in the same security group.

Unfortunately, tagging is not atomic with launching instances on EC2, so with this approach we have the possibility of spark-ec2 launching instances and crashing before they can be tagged, effectively orphaning those instances. The orphaned instances won't belong to any cluster, so the spark-ec2 script will be unable to clean them up.

Since this feature may still be worth supporting, there are several alternative approaches that we might consider, including detecting orphaned instances and logging warnings, or maybe using another mechanism to group instances into clusters. For the 1.1.0 release, though, I propose that we just revert this patch.

[JoshRosen]

Both patches reverted cleanly using git revert, but I'd still appreciate manual review to make sure I haven't broken anything. Going to test this shortly.

[SparkQA]

QA tests have started for PR 2225. This patch merges cleanly.
View progress: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/19546/consoleFull

[SparkQA]

QA results for PR 2225:
- This patch PASSES unit tests.
- This patch merges cleanly
- This patch adds no public classes

For more information see test ouptut:
https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/19546/consoleFull

[JoshRosen]

Since the original two commits, there were only two intervening commits to spark_ec2.py, c71b5c6 and 0c94a5b, both of which have the changes correctly preserved here.

(see https://github.com/JoshRosen/spark/commits/revert-ec2-cluster-naming/ec2/spark_ec2.py)

[shivaram]

LGTM. Hmm - This is unfortunate and something that I feared given the flaky experiences I have had with tags before. I checked the intervening commits too and the reverts look good to me.

Could you also manually test by launching a EC2 cluster just to be doubly sure ?

[JoshRosen]

I launched a cluster earlier using this version of the script and shut it down using the v1.0.2 one.

[nchammas]

FYI: It looks like branch-1.1 has an out-of-date version of run-tests-jenkins. Might want to update that.

[pwendell]

okay cool - let's merge this then (it isn't tested by jenkins anyways) although it would be nice to update that script in branch-1.1.

[nchammas]

it would be nice to update that script in branch-1.1

@pwendell I've done this in #2237.

[JoshRosen]

I've merged this into branch-1.1.