1. Copy stp-test.el and test.sh to the same directory.
2. Evaluate the .el file.
3. M-x global-auto-revert-mode.
4. M-x start-file-process-test.
5. See the message log. "sleeping done!" comes before "process done!".

Without step 3, "process done!" comes before "sleeping done!".

So it looks like, effectively, global-auto-revert-mode stops sleep-for
from calling process sentinels, at least.

I don't remember seeing anything like this in Emacs 25.

sit-for is not affected, BTW.

In GNU Emacs 26.0.50 (build 10, x86_64-pc-linux-gnu, GTK+ Version 3.20.9)
  of 2017-05-14 built on zappa
Repository revision: e6f64df9c2b443d3385c2c25c29ccd5283d37e3f
Windowing system distributor 'The X.Org Foundation', version 11.0.11804000
System Description:	Ubuntu 16.10