df -l not universally supported

[lrvick]

'df -l' is not supported in busybox based df which makes it difficult to run this package as a part of a minimal docker container.

See: https://github.com/osiegmar/cloudwatch-mon-scripts-python/blob/master/cloudwatchmon/cli/put_instance_stats.py#L368

[osiegmar]

I assume that the -l is not really required. Can you please try it without the -l and give me feedback if it works?

[lrvick]

Works fine for me without it.