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"
```
from moto.awslambda import models as lambda_models
from moto.apigateway import models as apigw_models
from moto.cloudformation import parsing, responses
from boto.cloudformation.stack import Output
from moto.cloudformation.exceptions import ValidationError, UnformattedGetAttTemplateException
from localstack import config
from localstack.constants import DEFAULT_PORT_CLOUDFORMATION_BACKEND, TEST_AWS_ACCOUNT_ID, MOTO_ACCOUNT_ID
from localstack.utils.aws import aws_stack, aws_responses
from localstack.utils.common import FuncThread, short_uid, recurse_object, clone, json_safe
from localstack.stepfunctions import models as sfn_models
from localstack.services.infra import (
    get_service_protocol, start_proxy_for_service, do_run, canonicalize_api_names)
from localstack.utils.bootstrap import setup_logging
from localstack.utils.cloudformation import template_deployer
from localstack.services.cloudformation import service_models
from localstack.services.awslambda.lambda_api import BUCKET_MARKER_LOCAL
LOG = logging.getLogger(__name__)
CURRENTLY_UPDATING_RESOURCES = {}
RUN_SERVER_IN_PROCESS = False
MODEL_MAP = {
    'AWS::StepFunctions::Activity': service_models.StepFunctionsActivity,
    'AWS::SNS::Subscription': service_models.SNSSubscription,
    'AWS::ApiGateway::GatewayResponse': service_models.GatewayResponse,
    'AWS::ApiGateway::Deployment': apigw_models.Deployment,
    'AWS::ApiGateway::Method': apigw_models.Method,
    'AWS::ApiGateway::Resource': apigw_models.Resource,
    'AWS::ApiGateway::RestApi': apigw_models.RestAPI,
    'AWS::StepFunctions::StateMachine': sfn_models.StateMachine
}
def start_cloudformation(port=None, asynchronous=False, update_listener=None):