Improve test case stability
Given unlucky timing, some of the new tests added by commit
bc32a12e0db2
can fail spuriously. We haven't seen such failures yet in buildfarm,
but allegedly we can prevent them with this tweak.
While at it, remove an unused injection point I (Álvaro) added.
Author: Mihail Nikalayeu <
[email protected]>
Discussion: https://postgr.es/m/CADzfLwUc=jtSUEaQCtyt8zTeOJ-gHZ8=w_KJsVjDOYSLqaY9Lg@mail.gmail.com
Discussion: https://postgr.es/m/CADzfLwV5oQq-Vg_VmG_o4SdL6yHjDoNO4T4pMtgJLzYGmYf74g@mail.gmail.com