wireguard: bump to 1.0.20201112

wireguard: bump to 1.0.20201112

* noise: take lock when removing handshake entry from table

This is a defense in depth patch backported from upstream to account for any
future issues with list node lifecycles.

* netns: check that route_me_harder packets use the right sk

A test for an issue that goes back to before Linux's git history began. I've
fixed this upstream, but it doesn't look possible to put it into the compat
layer, as it's a core networking problem. But we still test for it in the
netns test and warn on broken kernels.

* qemu: drop build support for rhel 8.2

We now test 8.3+.

* compat: SYM_FUNC_{START,END} were backported to 5.4
* qemu: bump default testing version

The real motivation for this version bump: 5.4.76 made a change that broke our
compat layer.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>