add timezone support

[yuriichv]

There is no ability to set timezone for consul docker container.
Add tzdata package, then the container can accept TZ env variable to set timezone.
Example:

docker run -e "TZ=Europe/Moscow" --rm consul date

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[eculver]

Can you please sign the CLA and resolve conflicts? We'd like to merge this if you're still willing.

[eculver]

FYI - I created #174 with this change.