…db, prevent pending-reboot on creation with parameter_group_name
* Add ModifyDBInstance call to CreateDBInstanceReadReplica if necessary
* Add RebootDBInstance call after ModifyDBInstance if necessary
* Refactor to not call update function during create function
* Additional acceptance testing with snapshot_identifier with allocated_storage, availability_zone, auto_minor_version_upgrade, and port
Previously:
```
--- FAIL: TestAccAWSDBInstance_SnapshotIdentifier_AllocatedStorage (1160.55s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'allocated_storage' expected "10", got "5"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_AllocatedStorage (1433.85s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'allocated_storage' expected "10", got "5"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_AutoMinorVersionUpgrade (1707.73s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'auto_minor_version_upgrade' expected "false", got "true"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_BackupRetentionPeriod (1336.28s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'backup_retention_period' expected "1", got "0"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_BackupWindow (1451.16s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'backup_window' expected "00:00-08:00", got "08:31-09:01"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_IamDatabaseAuthenticationEnabled (1525.07s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'iam_database_authentication_enabled' expected "true", got "false"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_MaintenanceWindow (1695.94s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'maintenance_window' expected "sun:01:00-sun:01:30", got "sat:07:22-sat:07:52"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_MultiAZ (1802.71s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'multi_az' expected "true", got "false"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_ParameterGroupName (1624.64s)
testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'parameter_group_name' expected "tf-acc-test-2677194822897355379", got "default.mysql5.7"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_VpcSecurityGroupIds (1479.95s)
testing.go:527: Step 0 error: After applying this step, the plan was not empty:
DIFF:
UPDATE: aws_db_instance.test
vpc_security_group_ids.1493394302: "" => "sg-0202c4194da544ffb"
vpc_security_group_ids.81746784: "sg-1ca59078" => ""
```
Before RebootDBInstance addition:
```
--- FAIL: TestAccAWSDBInstance_SnapshotIdentifier_ParameterGroupName (1256.87s)
testing.go:527: Step 0 error: Check failed: Check 5/5 error: expected DB Instance (tf-acc-test-8132994030462245505) Parameter Group (tf-acc-test-8132994030462245505) apply status to be: "in-sync", got: "pending-reboot"
--- FAIL: TestAccAWSDBInstance_ReplicateSourceDb_ParameterGroupName (1761.14s)
testing.go:527: Step 0 error: Check failed: Check 5/5 error: expected DB Instance (tf-acc-test-632112102194298217) Parameter Group (tf-acc-test-632112102194298217) apply status to be: "in-sync", got: "pending-reboot"
```