Comment 37 for bug 1671799

So this is being blocked by onscripter autopkgtests failing on qemu. Notes so far

- happens only with qemu
- test fails only if Xvfb was started from the same shell (as is the case with xvfb-run)
  - test runs fine if Xvfb was started from another shell..
  - trying to strace the test makes it pass..
- happens on Debian too
- tried reverting randr support from Xvfb, didn't help
- remaining two commits to it were for server internal abi changes, can't revert those