Fix cloudwatch alarm failure to create (#56)

[varunpalekar]

what

• Create multiple cloudwatch alarms for each node of cluster.

why

• You can't create a cloudwatch alarm on cluster, need to create on each node of cluster.

references

• closes #56

[osterman]

/test all

[joe-niland]

/terraform-fmt

[joe-niland]

/test all

[joe-niland]

@varunpalekar please have a look at this issue causing the tests to fail:

[varunpalekar]

/test all

[varunpalekar]

@joe-niland Thanks for the review. I updated the code respectively. I also find an issue when running on a new infra, also fixed that.

[joe-niland]

/test all

[joe-niland]

Thanks for your contribution @varunpalekar. Released as https://github.com/cloudposse/terraform-aws-elasticache-redis/releases/tag/0.23.0