Geo: Move geo internal url declarations into common vars

What does this MR do?

Moves geo_primary_internal_url and geo_secondary_internal_url into common_vars. Variables declared in inventories won't overwrite ones defined inside the playbook, but they will overwrite ones defined in the common_vars dependency.

Closes #519 (closed)

Related issues

Author's checklist

When ready for review, the Author applies the workflowready for review label and mention @gl-quality/get-maintainers:

• Merge request:
  • Corresponding Issue raised and reviewed by the GET maintainers team.
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  • MR targeting the appropriate branch
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• Code:
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  • Documentation created/updated in the same MR.
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