degraded systemd status due to nf_conntrack_ipv4,ipv6 module after kernel upgrade

[Nobuto Murata]

It's related bug #1834213 and the commit[1], but a follow-up one for upgrade.

[1] https://review.opendev.org/gitweb?p=openstack%2Fcharm-neutron-openvswitch.git;a=commitdiff;h=b76a59299794700fae1878af513c90ca5182a9f6

How to reproduce:
1. install neutron-openvswith charm with bionic GA kernel (4.15) and firewall-driver=openvswitch
2. after installation completed, install hwe or hwe-edge kernel which do not have nf_conntrack_ipv4 or ipv6 modules
3. reboot

The theory here is that the charm will load and write nf_conntrack_ipv4 and ipv6 module into /etc/modules when those modules are available at the time of install (GA kernel in this case). We might be missing some considerations on the upgrade path of kernel, but forcing those two modules loaded even after a kernel upgrade while nf_conntrack module should be sufficient as the patch states.

[Nobuto Murata (nobuto)]

$ cat /etc/modules
# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.

nf_conntrack_ipv4
nf_conntrack_ipv6

$ sudo systemctl status
● myhost
    State: degraded
     Jobs: 0 queued
   Failed: 1 units
    Since: Fri 2019-11-08 07:27:08 UTC; 7min ago

$ sudo systemctl --failed
  UNIT LOAD ACTIVE SUB DESCRIPTION
● systemd-modules-load.service loaded failed failed Load Kernel Modules

$ sudo systemctl status systemd-modules-load.service
● systemd-modules-load.service - Load Kernel Modules
   Loaded: loaded (/lib/systemd/system/systemd-modules-load.service; static; vendor preset: enabled)
   Active: failed (Result: exit-code) since Fri 2019-11-08 07:27:08 UTC; 8min ago
     Docs: man:systemd-modules-load.service(8)
           man:modules-load.d(5)
  Process: 543 ExecStart=/lib/systemd/systemd-modules-load (code=exited, status=1/FAILURE)
 Main PID: 543 (code=exited, status=1/FAILURE)

Nov 08 07:27:08 polite-weasel systemd-modules-load[543]: Failed to find module 'nf_conntrack_ipv4'
Nov 08 07:27:08 polite-weasel systemd-modules-load[543]: Failed to find module 'nf_conntrack_ipv6'
Nov 08 07:27:08 polite-weasel systemd-modules-load[543]: Inserted module 'iscsi_tcp'
Nov 08 07:27:08 polite-weasel systemd-modules-load[543]: Inserted module 'ib_iser'
Nov 08 07:27:08 polite-weasel systemd[1]: systemd-modules-load.service: Main process exited, code=exited, status=1/FAILURE
Nov 08 07:27:08 polite-weasel systemd[1]: systemd-modules-load.service: Failed with result 'exit-code'.
Nov 08 07:27:08 polite-weasel systemd[1]: Failed to start Load Kernel Modules.
Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.