The problem was that the fixes had us generating TLS certs with a
2-day lifetime on the assumption that we'd rotate fairly often. In
fact, we never rotate our TLS keys.
This patch fixes the situation in 2 ways:
1. It bumps the default lifetime back up to one year until we get
rotation in place.
2. It changes tor_tls_context_new() so that it doesn't leak memory
when you call it more than once.
svn:r663