various: Improve error reporting if missing file server module on 0.12 If there is some error loading net.http.files then it would be swallowed by the pcall and then it would proceed to trying mod_http_files, which might cause unexpected behavior on 0.12 Ref #1765

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summary: Extra verbose stanza logging
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Summary
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This module logs the full stanzas that are sent and received into debug
logs, for debugging purposes.