As an enhancement to https://github.com/localstack/localstack/pull/1194

It would be really helpful to send the Lambda name, either as data, a header, or as part of the URL.

At code location: https://github.com/localstack/localstack/blob/03c6f4bf250edd18eb818ed65090f508636b0bff/localstack/services/awslambda/lambda_api.py#L696

I can likely open a PR to handle this given some feedback on the feature and potential design.

Right now all I see is the following (using `npx http-echo-server`):
```
[socket#8] event: data
--> POST / HTTP/1.1
--> Host: 192.168.1.x:3000
--> User-Agent: python-requests/2.22.0
--> Accept-Encoding: gzip, deflate
--> Accept: */*
--> Connection: keep-alive
--> Content-Length: 9
--> Content-Type: application/x-www-form-urlencoded
-->
-->
[socket#8] event: data
--> Name=test
```
def test_invocation_type_dry_run(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_PY, Payload=b'{}',
            InvocationType='DryRun')
        self.assertEqual(result['StatusCode'], 204)
    def test_lambda_environment(self):
        vars = {'Hello': 'World'}
        testutil.create_lambda_function(handler_file=TEST_LAMBDA_ENV, libs=TEST_LAMBDA_LIBS,
                                        func_name=TEST_LAMBDA_NAME_ENV, runtime=LAMBDA_RUNTIME_PYTHON27, envvars=vars)
        
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_ENV, Payload=b'{}')
        result_data = result['Payload']
        self.assertEqual(result['StatusCode'], 200)
        self.assertDictEqual(json.load(result_data), vars)
        
        result = self.lambda_client.get_function_configuration(
            FunctionName=TEST_LAMBDA_NAME_ENV)
        self.assertEqual(result['Environment'], {'Variables': vars})
        
        testutil.delete_lambda_function(TEST_LAMBDA_NAME_ENV)
    def test_invocation_with_qualifier(self):
        lambda_name = 'test_lambda_%s' % short_uid()
        bucket_name = 'test-bucket-lambda2'
        bucket_key = 'test_lambda.zip'
        
        zip_file = testutil.create_lambda_archive(
            load_file(TEST_LAMBDA_PYTHON), get_content=True,
            libs=TEST_LAMBDA_LIBS, runtime=LAMBDA_RUNTIME_PYTHON27)
        self.s3_client.create_bucket(Bucket=bucket_name)