Metadata: get_client_names_by_* fixes

Fixed long lines.

Improved efficiency by avoiding multiple loops over the same data.
SSLServer: Removed decode_request_content call

decode_request_content() just adds support for gzipped content, which
the Bcfg2 client doesn't support.  Given that this feature was only
added in Python 2.7, it's unlikely we'll be adding support for gzipped
POST content any time soon.
SSLServer: close connections properly
Rules: fixed HandlesEntry for XMLSrc replacement

This makes HandlesEntry work with the new code that's in place for
StructFile to replace XMLSrc.  Fixes
https://github.com/Bcfg2/bcfg2/commit/2169edc1bba82076db776b75db89b79d6f2f4786#commitcomment-3968162
Revert "Rules: fixed HandlesEntry for XMLSrc replacement"

This reverts commit 542ededa8297b1889542d97b9bdfb8345dd7550c.

Committed to wrong branch.