package/docker-proxy: bump version to 55685ba49593
Which is the version used by docker 18.09.9:
https://github.com/docker/engine/commit/0a3767c7e9803f0a595a07b0548e99d60e861062
Also add a hash for the license file.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>