When trying to deploy a serverless service that does not currently deploy correctly onto localstack using a custom deployment bucket, the lambdas seems to be created regardless (???) but not as part of the stack, with localstack outputting `botocore.errorfactory.ResourceConflictException: An error occurred (ResourceConflictException) when calling the CreateFunction operation: Function already exist` .

For example, the `serverless.yml` below would currently fail to deploy due to  #1676 , but because a `deploymentBucket` was added, it will instead fail due to `Function already exist`. Subsequently removing `deploymentBucket` or even `events` from the the file will not allow it to deploy - it will fail until localstack is restarted ( or until the lambda is manually deleted?).

I've also reproduced this with services suffering from #1675. 

```yaml
service: "localtest"

provider:
  name: "aws"
  runtime: "nodejs10.x"
  deploymentBucket:
    name: "testbucket"

functions:
  hello:
    handler: "handler.hello"
    events:
      - schedule: "cron(0 * * * ? *)"

plugins:
- "serverless-localstack"

custom:
  localstack:
    stages:
      - "local"
```
result = SNS_Topic_get_cfn_attribute(self, attribute_name)
        if attribute_name.lower() in ['arn', 'topicarn']:
            result = aws_stack.fix_account_id_in_arns(result)
        return result
    IAM_Role_get_cfn_attribute_orig = iam_models.Role.get_cfn_attribute
    iam_models.Role.get_cfn_attribute = IAM_Role_get_cfn_attribute
    
    @classmethod
    def Lambda_create_from_cloudformation_json(cls, resource_name, cloudformation_json, region_name):
        resource_name = cloudformation_json.get('Properties', {}).get('FunctionName') or resource_name
        return Lambda_create_from_cloudformation_json_orig(resource_name, cloudformation_json, region_name)
    Lambda_create_from_cloudformation_json_orig = lambda_models.LambdaFunction.create_from_cloudformation_json
    lambda_models.LambdaFunction.create_from_cloudformation_json = Lambda_create_from_cloudformation_json
    
    @classmethod
    def Mapping_create_from_cloudformation_json(cls, resource_name, cloudformation_json, region_name):
        props = cloudformation_json.get('Properties', {})
        func_name = props.get('FunctionName') or ''
        if ':lambda:' in func_name:
            props['FunctionName'] = aws_stack.lambda_function_name(func_name)
        return Mapping_create_from_cloudformation_json_orig(resource_name, cloudformation_json, region_name)
    Mapping_create_from_cloudformation_json_orig = lambda_models.EventSourceMapping.create_from_cloudformation_json
    lambda_models.EventSourceMapping.create_from_cloudformation_json = Mapping_create_from_cloudformation_json
    
    @classmethod
    def Lambda_update_from_cloudformation_json(cls,