Fallback to previous image if unable to download latest

[abrooksv]

Description:

Steps to reproduce the issue:

1. Turn off internet, run without ---skip-pull-image
2. Crashes

Expected result:
If we have a cached image, SAM should use that and report that it failed to download the latest

Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

Output of sam --version:
0.6.0

Optional Debug logs:

2018-09-26 16:07:50 Decompressing /var/folders/q5/cfv4k63519vcllnnpwz5zsj0wnjvck/T/5546671975416044841.zip
Traceback (most recent call last):
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/docker/api/client.py", line 229, in _raise_for_status
    response.raise_for_status()
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/requests/models.py", line 939, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 500 Server Error: Internal Server Error for url: http+docker://localhost/v1.35/images/create?tag=java8&fromImage=lambci%2Flambda

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/alfredbr/Library/Python/3.7/bin/sam", line 11, in <module>
    sys.exit(cli())
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/click/decorators.py", line 64, in new_func
    return ctx.invoke(f, obj, *args[1:], **kwargs)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/samcli/commands/local/invoke/cli.py", line 49, in cli
    docker_volume_basedir, docker_network, log_file, skip_pull_image, profile, region)  # pragma: no cover
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/samcli/commands/local/invoke/cli.py", line 90, in do_cli
    stderr=context.stderr)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/samcli/commands/local/lib/local_lambda.py", line 80, in invoke
    self.local_runtime.invoke(config, event, debug_context=self.debug_context, stdout=stdout, stderr=stderr)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/samcli/local/lambdafn/runtime.py", line 79, in invoke
    self._container_manager.run(container)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/samcli/local/docker/manager.py", line 53, in run
    self.pull_image(image_name)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/samcli/local/docker/manager.py", line 83, in pull_image
    result_itr = self.docker_client.api.pull(image_name, stream=True, decode=True)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/docker/api/image.py", line 399, in pull
    self._raise_for_status(response)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/docker/api/client.py", line 231, in _raise_for_status
    raise create_api_error_from_http_exception(e)
  File "/Users/alfredbr/Library/Python/3.7/lib/python/site-packages/docker/errors.py", line 31, in create_api_error_from_http_exception
    raise cls(e, response=response, explanation=explanation)
docker.errors.APIError: 500 Server Error: Internal Server Error ("Get https://registry-1.docker.io/v2/: Service Unavailable")

[jfuss]

Duplicate of #529 and #451

Closing