provider/aws: Fix ES Domain acceptance tests

[radeksimko]

Why are tests failing?

See context in #13157 (comment)

Here is a snippet from a debug log before 23rd March:

---[ REQUEST POST-SIGN ]-----------------------------
POST /2015-01-01/es/domain HTTP/1.1
Host: es.us-west-2.amazonaws.com
User-Agent: aws-sdk-go/1.7.9 (go1.8; linux; amd64) APN/1.0 HashiCorp/1.0 Terraform/0.9.2-dev
Content-Length: 72
Authorization: *REDACTED*
X-Amz-Date: 20170322T061231Z
Accept-Encoding: gzip

{"DomainName":"tf-test-530907444151386247","ElasticsearchVersion":"2.3"}
--
2017/03/22 06:12:32 [DEBUG] [aws-sdk-go] DEBUG: Response es/CreateElasticsearchDomain Details:
---[ RESPONSE ]--------------------------------------
HTTP/1.1 200 OK
Content-Length: 734
Content-Type: application/json
Date: Wed, 22 Mar 2017 06:12:32 GMT
X-Amzn-Requestid: *REDACTED*

{"DomainStatus":{"ARN":"arn:aws:es:us-west-2:*REDACTED*:domain/tf-test-530907444151386247","AccessPolicies":"","AdvancedOptions":{"rest.action.multi.allow_explicit_index":"true"},"Created":true,"Deleted":false,"DomainId":"*REDACTED*/tf-test-530907444151386247","DomainName":"tf-test-530907444151386247","EBSOptions":{"EBSEnabled":false,"EncryptionEnabled":null,"Iops":null,"VolumeSize":null,"VolumeType":null},"ElasticsearchClusterConfig":{"DedicatedMasterCount":null,"DedicatedMasterEnabled":false,"DedicatedMasterType":null,"InstanceCount":1,"InstanceType":"m3.medium.elasticsearch","ZoneAwarenessEnabled":false},"ElasticsearchVersion":"2.3","Endpoint":null,"Processing":true,"SnapshotOptions":{"AutomatedSnapshotStartHour":0}}}
-----------------------------------------------------

and snippet from this morning:

2017/03/29 06:14:14 [DEBUG] [aws-sdk-go] DEBUG: Request es/CreateElasticsearchDomain Details:
---[ REQUEST POST-SIGN ]-----------------------------
POST /2015-01-01/es/domain HTTP/1.1
Host: es.us-west-2.amazonaws.com
User-Agent: aws-sdk-go/1.7.9 (go1.8; linux; amd64) APN/1.0 HashiCorp/1.0 Terraform/0.9.3-dev
Content-Length: 73
Authorization: *REDACTED*
X-Amz-Date: 20170329T061414Z
Accept-Encoding: gzip

{"DomainName":"tf-test-4999745254680115254","ElasticsearchVersion":"2.3"}
-----------------------------------------------------
2017/03/29 06:14:15 [DEBUG] [aws-sdk-go] DEBUG: Response es/CreateElasticsearchDomain Details:
---[ RESPONSE ]--------------------------------------
HTTP/1.1 400 Bad Request
Content-Length: 69
Content-Type: application/json
Date: Wed, 29 Mar 2017 06:14:15 GMT
X-Amzn-Errortype: ValidationException
X-Amzn-Requestid: *REDACTED*

{"message":"EBS storage must be selected for m4.large.elasticsearch"}
-----------------------------------------------------

Why make volume_type Computed?

Volume type seems to default to gp2 (general purpose SSD) on the API side if not defined but I was unable to verify from available docs this is the case for all instance types and I wanted to avoid making it Default anyway because the ebs_options block may not be defined at all or ebs_enabled may be false in which case this should be empty.

Test plan

make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSElasticSearchDomain'

=== RUN   TestAccAWSElasticSearchDomainPolicy_basic
--- PASS: TestAccAWSElasticSearchDomainPolicy_basic (3527.08s)
=== RUN   TestAccAWSElasticSearchDomain_basic
--- PASS: TestAccAWSElasticSearchDomain_basic (1384.46s)
=== RUN   TestAccAWSElasticSearchDomain_importBasic
--- PASS: TestAccAWSElasticSearchDomain_importBasic (1373.07s)
=== RUN   TestAccAWSElasticSearchDomain_v23
--- PASS: TestAccAWSElasticSearchDomain_v23 (1509.51s)
=== RUN   TestAccAWSElasticSearchDomain_tags
--- PASS: TestAccAWSElasticSearchDomain_tags (1408.22s)

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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