When initializing Providers with variables we have to set the default values not empty

[xescugc]

General information:

• Operating System:
• Terracognita version / tag:
• Did you build Terracognita from sources or did you use the Docker image:

Describe the bug:

When we initialize a provider block we set the required values with variables and those are empty, but on the provider definition those values could have functions which set the default values so we should use them instead of setting it empty.

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Additional context

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