resource/aws_glue_catalog_database: Prevent error when deleted outside Terraform

[bflad]

Fixes #5136

Changes proposed in this pull request:

• Ignore EntityNotFoundException in exists function for aws_glue_catalog_database resource

Previously:

make testacc TEST=./aws TESTARGS='-run=TestAccAWSGlueCatalogDatabase_recreates'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./aws -v -run=TestAccAWSGlueCatalogDatabase_recreates -timeout 120m
=== RUN   TestAccAWSGlueCatalogDatabase_recreates
--- FAIL: TestAccAWSGlueCatalogDatabase_recreates (10.99s)
	testing.go:518: Step 1 error: Error refreshing: 1 error(s) occurred:

		* aws_glue_catalog_database.test: 1 error(s) occurred:

		* aws_glue_catalog_database.test: aws_glue_catalog_database.test: EntityNotFoundException: Database my_test_catalog_database_6550552809316099925 not found.
			status code: 400, request id: 4080a81b-8455-11e8-8ae0-d76c07653239
FAIL
FAIL	github.com/terraform-providers/terraform-provider-aws/aws	11.031s
make: *** [testacc] Error 1

Output from acceptance testing:

$ make testacc TEST=./aws TESTARGS='-run=TestAccAWSGlueCatalogDatabase'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./aws -v -run=TestAccAWSGlueCatalogDatabase -timeout 120m
=== RUN   TestAccAWSGlueCatalogDatabase_importBasic
--- PASS: TestAccAWSGlueCatalogDatabase_importBasic (14.76s)
=== RUN   TestAccAWSGlueCatalogDatabase_full
--- PASS: TestAccAWSGlueCatalogDatabase_full (27.74s)
=== RUN   TestAccAWSGlueCatalogDatabase_recreates
--- PASS: TestAccAWSGlueCatalogDatabase_recreates (12.46s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	55.008s

[tombuildsstuff]

LGTM 👍🏼

[bflad]

This has been released in version 1.27.0 of the AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[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.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!