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"
```
original_resource, new_resource_name, cloudformation_json, region_name):
        resource_name = cloudformation_json.get('Properties', {}).get('FunctionName') or new_resource_name
        return Lambda_create_from_cloudformation_json_orig(resource_name, cloudformation_json, region_name)
    if not hasattr(lambda_models.LambdaFunction, 'update_from_cloudformation_json'):
        lambda_models.LambdaFunction.update_from_cloudformation_json = Lambda_update_from_cloudformation_json
    
    def depl_delete_from_cloudformation_json(
            resource_name, resource_json, region_name):
        properties = resource_json['Properties']
        LOG.info('TODO: apigateway.Deployment.delete_from_cloudformation_json %s' % properties)
    if not hasattr(apigw_models.Deployment, 'delete_from_cloudformation_json'):
        apigw_models.Deployment.delete_from_cloudformation_json = depl_delete_from_cloudformation_json
    
    def vers_delete_from_cloudformation_json(
            resource_name, resource_json, region_name):
        properties = resource_json['Properties']
        LOG.info('TODO: apigateway.Deployment.delete_from_cloudformation_json %s' % properties)
    if not hasattr(lambda_models.LambdaVersion, 'delete_from_cloudformation_json'):
        lambda_models.LambdaVersion.delete_from_cloudformation_json = vers_delete_from_cloudformation_json
    
    @classmethod
    def RestAPI_create_from_cloudformation_json(cls, resource_name, cloudformation_json, region_name):