Increase HS desc cert lifetime.

We used to have a small HS desc cert lifetime but those certs can stick
around for 36 hours if they get initialized in the beginning of overlap
period.

[warn] Bug: Non-fatal assertion !(hs_desc_encode_descriptor(desc->desc, &desc->signing_kp, &encoded_desc) < 0) failed in
upload_descriptor_to_hsdir at src/or/hs_service.c:1886. Stack trace: (on Tor 0.3.2.0-alpha-dev b4a14555597fb9b3)