Revert "When hijacking events, don't let the user thread that was allowed"
This reverts commit a8af467fad7e5fff71643a3d6f2d06ac4f637e66.
This was a follow-on to 97572c1860efeeb97b5940927cee72081b61810a which was me
trying to guess why the ubuntu bots were failing with an entirely unhelpful
failure mode. I'll have to figure out how I can reproduce this somewhere so
I can look at it for real.