The limits were only written back after a successful body, so a
failing limit test left the shared kernel at the lowered values and
every later run failed with ENOSPC. The helper now restores in a
`defer` and can lower a chosen subset of the limits.
inotify exposes a /proc interface to limit kernel memory usage. If those
limits are set too low, inotify cannot add all watches. The integration
test verifies, that Inotify yields an error in that case.
T. R. Bernstein