Set default siteinfo URLs and update loaded log message

[stephen-soltesz]

When beginning to integrate siteinfo reloading into the etl_worker I discovered two things:

• the log message from sites.go is confusing b/c it was reporting the total number of networks as sites.
• the empty siteinfo URLs caused a segfault when trying to read them during loading.

This change adds site counting during load and updates the log message to report on site count and network counts. This change also adds default values for the siteinfo URLs using the production URLs. This is almost always the value we want, and the site package unit tests override these values already.

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 2555

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 71.89%

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Totals
Change from base Build #2178:	0.01%
Covered Lines:	1647
Relevant Lines:	2291

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💛 - Coveralls

[stephen-soltesz]

Thank you!