v1.2.1

This is a patch release that fixes bugs in the new host and wallet. This release also includes a fix for a security vulnerability that especially impacts hosts.

The first time you unlock the wallet should be moderately faster, especially on HDDs.

If you are upgrading a host from v1.1.2 to v1.2.1, the upgrade will be significantly faster compared to upgrading from v1.1.2 to v1.2.0. It can still take 6-12 hours for larger hosts, but previous upgrade times of several days should no longer happen.

A siac renter allowance cancel command was also added for canceling your current allowance.

Thanks to @mtlynch for contributing to this release! And also thanks to the contributor (kept anonymous) who discovered and responsibly disclosed the security vulnerability.