Certificate fingerprint seems to have left-padding zeroes removed

(originally filed as https://github.com/martinpaljak/M2Crypto/issues/38)

I'm having an issue right now where I have an original fingerprint calculated using:

fingerprint = cert.get_fingerprint(md='sha1').lower()

However, I later calculate it myself during certificate-based authentication. I just ran into a situation where a certificate wasn't found because the M2Crypto version had a leading zero that was removed.