runc run [timens with no offsets] is flaky on ubuntu

[kolyshkin]

Seen this failure twice already:

not ok 184 runc run [timens with no offsets]
# (in test file tests/integration/timens.bats, line 37)
#   `grep -E '^monotonic\s+0\s+0$' <<<"$output"' failed
# runc spec --rootless (status=0):
#
# runc run test_busybox (status=0):
# monotonic           0         0

# boottime            0         0

I stared at the code and it looks just fine, yet grep fails. I suspect a problem with grep (or me).

[kolyshkin]

recent failure: https://github.com/opencontainers/runc/actions/runs/6515923317/job/17698880038?pr=4073

[kolyshkin]

OK, this looks similar to #4029, and the undelying reason is probably #2425 (see also #4029 (comment))

[kolyshkin]

Alas, we can't use the same fix as in #4095. Maybe it's a sign we should fix the underlying issue.