Bridge descriptor sanitizer calculates wrong descriptor digest
When determining SHA-1 hashes of sanitized bridge descriptors in metrics-db we don't include the "router-signature" line. That means we store sanitized bridge descriptors under the wrong file name and reference them from bridge network statuses using the wrong descriptor identifier. The same applies to extra-info digests.
This bug isn't problematic as long as one uses descriptor file names to navigate between network statuses, server descriptors, and extra-info descriptors. But navigating doesn't work anymore when using metrics-lib's getServerDescriptorDigest() or getExtraInfoDigest() methods which calculate the SHA-1 digest correctly. We should fix this bug and sanitize all bridge descriptors again.