* fix: disable debianrepo build on master branch
This just mitigates https://github.com/ooni/probe/issues/1741 and does
not fully address it, but I'd rather avoid delving into this problem until
I open a release/v3.11.0 branch and have to really fix this issue.
* fix: only run coverage using go1.17
This is the version of Go with which we are going to bless v3.11.0
therefore it's the only version of Go that matters.
Reference issue: https://github.com/ooni/probe/issues/1738.
* fix(ptx/obfs4_test.go): avoid context-vs-normal-code race
We want to test whether we get the context failure if the error
generated inside normal code happens _after_ the context cancellation.
The best way to do that is to write code that is not racy. To this
end, we just need to pause normal code until we know that the context
has returned to the caller. We also need to ensure we do not leak
a goroutine, hence we use a WaitGroup to check that.
Fixes https://github.com/ooni/probe/issues/1750
