[x] bug report
[ ] feature request

# Detailed description
`lambda_executor.py` current retrieves the container entrypoint from the docker image via `docker inspect --format="{{ .ContainerConfig.Entrypoint }}" ..`. This is fragile and may be missing depending on how the image in question is built. There is a `config` block _and_ a `containerconfig` block that are mostly the same, but sometimes different depending what built and what version of that thing built the image, for example we are seeing the entrypoint missing on images built with Docker for Mac 2.5.0.1, but not on earlier versions, others using `podman` are noticing the fragility in other projects:

https://github.com/containers/podman/issues/2017

## Expected behavior
entrypoint value is picked up from a validly built container

## Actual behavior
entrypoint is sometimes an empty string, which then for a `provided` lambda executor ends up with a script error trying to execute the handler name.

The simple fix is to change `--format="{{ .ContainerConfig.Entrypoint }}"` to `--format="{{ .Config.Entrypoint }}"` which seems like the more canonical way of getting that value.



┆Issue is synchronized with this [Jira Task](https://localstack.atlassian.net/browse/LOC-54) by [Unito](https://www.unito.io/learn-more)

save_file(os.path.join(lambda_cwd, events_file), event_body)
            classpath = Util.get_java_classpath(target_file)
            command = ("bash -c 'cd %s; java %s -cp \"%s\" \"%s\" \"%s\" \"%s\"'" %
                (taskdir, java_opts, classpath, LAMBDA_EXECUTOR_CLASS, handler, events_file))
        
        if is_nodejs_runtime(runtime):
            environment['NODE_TLS_REJECT_UNAUTHORIZED'] = '0'
        
        cmd = self.prepare_execution(func_arn, environment, runtime, command, handler, lambda_cwd)
        
        LOG.info('Running lambda cmd: %s' % cmd)
        result = self.run_lambda_executor(cmd, stdin, env_vars=environment, func_details=func_details)
        
        events_file and os.path.exists(events_file) and rm_rf(events_file)
        return result
class LambdaExecutorReuseContainers(LambdaExecutorContainers):
    """ Executor class for executing Lambda functions in re-usable Docker containers """
    def __init__(self):
        super(LambdaExecutorReuseContainers, self).__init__()
        
        self.docker_container_lock = threading.RLock()
        
        
        
        
        self.next_port = 0
        self.max_port = LAMBDA_SERVER_UNIQUE_PORTS
        self.port_offset = LAMBDA_SERVER_PORT_OFFSET
    def prepare_execution(self, func_arn, env_vars, runtime, command, handler, lambda_cwd):