added missing parameter to docker run command

[tyron]

Sample docker run command was missing the -v (--volume) parameter on the sample code

VIC Appliance Checklist:

• Up to date with master branch
• Added tests
• Considered impact to upgrade
• Tests passing
• Updated documentation
• Impact assessment checklist

If this is a feature or change to existing functionality, consider areas of impact with the Impact
Assessment Checklist

Fixes #

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