ubuntu_loop_smoke_test timeout on google instance n2d-standard-2/n2d-standard-64

[Po-Hsu Lin]

Issue found on these 2 specific google instances n2d-standard-2 / n2d-standard-64 with:
  * GKE 5.4.0-1078.84
  * GKE 5.15.0-1011.14~20.04.1
  * GCP 5.4.0-1084.92
  * GCP 5.15.0-1013.18~20.04.1

Manual test on n2d-standard-64 with GKE 5.15.0-1011.14~20.04.1 shows this test will take about 70 minutes to run:
        START ubuntu_loop_smoke_test.loop-smoke-test ubuntu_loop_smoke_test.loop-smoke-test timestamp=1657868687 localtime=Jul 15 07:04:47
 Persistent state client._record_indent now set to 2
 Persistent state client.unexpected_reboot now set to ('ubuntu_loop_smoke_test.loop-smoke-test', 'ubuntu_loop_smoke_test.loop-smoke-test')
 System python is too old, crash handling disabled
 Running '/home/google/autotest/client/tmp/ubuntu_loop_smoke_test/src/loop-test'
 [stdout] created 1024 out of 1024 loop back devices in 368.418033 seconds
 [stdout] 0 loop read failures
 [stdout] delelete 1024 out of 1024 loop back devices in 3596.712889 seconds
 [stdout] PASSED
                GOOD ubuntu_loop_smoke_test.loop-smoke-test ubuntu_loop_smoke_test.loop-smoke-test timestamp=1657872839 localtime=Jul 15 08:13:59 completed successfully
        END GOOD ubuntu_loop_smoke_test.loop-smoke-test ubuntu_loop_smoke_test.loop-smoke-test timestamp=1657872839 localtime=Jul 15 08:13:59
 Persistent state client._record_indent now set to 1
 Persistent state client.unexpected_reboot deleted
 END GOOD ---- ---- timestamp=1657872840 localtime=Jul 15 08:14:00

[Po-Hsu Lin (cypressyew)]

Test shows:
  * 55 min - f-gcp-5.4 + n2d-standard-2
  * 48 min - f-gcp-5.4 + n2d-standard-64
  * 55 min - f-gke-5.4 + n2d-standard-2
  * 48 min - f-gke-5.4 + n2d-standard-64
  * 36 min - f-gcp-5.15 + n2d-standard-2
  * 72 min - f-gcp-5.15 + n2d-standard-64
  * 69 min - f-gke-5.15 + n2d-standard-64

[Po-Hsu Lin (cypressyew)]

https://git.launchpad.net/~canonical-kernel-team/+git/autotest-client-tests/commit/?id=95dd2445d265f025c47037e0c50d18238d2a7b2d