t/db_instance: Run acceptance tests in default region

[radeksimko]

The tests were pinned to us-east-1 for (IMO) no particular reason in hashicorp/terraform#3853

This is to address the following test failures:

=== RUN   TestAccAWSDBInstanceNoSnapshot
--- FAIL: TestAccAWSDBInstanceNoSnapshot (6.84s)
    testing.go:503: Step 0 error: Error applying: 1 error(s) occurred:
        
        * aws_db_instance.snapshot: 1 error(s) occurred:
        
        * aws_db_instance.snapshot: Error creating DB Instance: InsufficientDBInstanceCapacity: Cannot create a db.t2.micro database instance because there are no availability zones with sufficient capacity for non-VPC and storage type : standard for db.t2.micro. Please try the request again at a later time.
            status code: 400, request id: 7f3d6248-2bfc-427a-8e26-57037084c33e
=== RUN   TestAccAWSDBInstanceSnapshot
--- FAIL: TestAccAWSDBInstanceSnapshot (6.64s)
    testing.go:503: Step 0 error: Error applying: 1 error(s) occurred:
        
        * aws_db_instance.snapshot: 1 error(s) occurred:
        
        * aws_db_instance.snapshot: Error creating DB Instance: InsufficientDBInstanceCapacity: Cannot create a db.t2.micro database instance because there are no availability zones with sufficient capacity for non-VPC and storage type : standard for db.t2.micro. Please try the request again at a later time.
            status code: 400, request id: 9f67a929-1e4a-4883-b33b-ad0bc73d353b

I also added one test which still runs in us-east-1 but only tests basic functionality in that region and doesn't overlap with tests which are supposed to test something else. I had to choose db.m3.medium as it was the cheapest size from m3 family available in that region. t2 seems to be constantly unavailable in the region.

Test results

=== RUN   TestAccAWSDBInstance_ec2Classic
--- PASS: TestAccAWSDBInstance_ec2Classic (448.96s)
=== RUN   TestAccAWSDBInstance_generatedName
--- PASS: TestAccAWSDBInstance_generatedName (398.72s)
=== RUN   TestAccAWSDBInstance_MinorVersion
--- PASS: TestAccAWSDBInstance_MinorVersion (417.60s)
=== RUN   TestAccAWSDBInstance_namePrefix
--- PASS: TestAccAWSDBInstance_namePrefix (418.55s)
=== RUN   TestAccAWSDBInstance_diffSuppressInitialState
--- PASS: TestAccAWSDBInstance_diffSuppressInitialState (418.55s)
=== RUN   TestAccAWSDBInstance_iamAuth
--- PASS: TestAccAWSDBInstance_iamAuth (470.62s)
=== RUN   TestAccAWSDBInstance_importBasic
--- PASS: TestAccAWSDBInstance_importBasic (470.84s)
=== RUN   TestAccAWSDBInstance_basic
--- PASS: TestAccAWSDBInstance_basic (478.79s)
=== RUN   TestAccAWSDBInstance_portUpdate
--- PASS: TestAccAWSDBInstance_portUpdate (513.97s)
=== RUN   TestAccAWSDBInstance_kmsKey
--- PASS: TestAccAWSDBInstance_kmsKey (520.18s)
=== RUN   TestAccAWSDBInstance_optionGroup
--- PASS: TestAccAWSDBInstance_optionGroup (553.10s)
=== RUN   TestAccAWSDBInstance_noSnapshot
--- PASS: TestAccAWSDBInstance_noSnapshot (571.47s)
=== RUN   TestAccAWSDBInstance_enhancedMonitoring
--- PASS: TestAccAWSDBInstance_enhancedMonitoring (583.22s)
=== RUN   TestAccAWSDBInstance_subnetGroup
--- PASS: TestAccAWSDBInstance_subnetGroup (785.42s)
=== RUN   TestAccAWSDBInstance_snapshot
--- PASS: TestAccAWSDBInstance_snapshot (965.69s)
=== RUN   TestAccAWSDBInstance_replica
--- PASS: TestAccAWSDBInstance_replica (1411.09s)
=== RUN   TestAccAWSDBInstance_MSSQL_TZ
--- PASS: TestAccAWSDBInstance_MSSQL_TZ (2299.56s)

[tombuildsstuff]

LGTM 👍

[ghost]

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