[oooq] sshd not starting on overcloud nodes

[Lewis Denny]

On a fresh deployment of oooq master branch openssh not starting due to the following error:
```
Unable to load host key: /etc/ssh/ssh_host_rsa_key
Unable to load host key: /etc/ssh/ssh_host_ecdsa_key
Unable to load host key: /etc/ssh/ssh_host_ed25519_key
sshd: no hostkeys available -- exiting.
```

sshd-keygen.target creates the host keys on first boot or if they are ever removed by calling `/usr/libexec/openssh/sshd-keygen` and passing it a single argument of key type:
```
[root@overcloud-controller-0 ~]# systemctl cat sshd-keygen.target
# /usr/lib/systemd/system/sshd-keygen.target
[Unit]
<email address hidden>
<email address hidden>
<email address hidden>
PartOf=sshd.service
```

```
[root@overcloud-controller-0 ~]# systemctl cat <email address hidden>
# /usr/lib/systemd/system/sshd-keygen@.service
[Unit]
Description=OpenSSH %i Server Key Generation
ConditionFileNotEmpty=|!/etc/ssh/ssh_host_%i_key

[Service]
Type=oneshot
EnvironmentFile=-/etc/sysconfig/sshd
ExecStart=/usr/libexec/openssh/sshd-keygen %i

[Install]
WantedBy=sshd-keygen.target

# /etc/systemd/system/sshd-keygen@.service.d/disable-sshd-keygen-if-cloud-init-active.conf

# In some cloud-init enabled images the sshd-keygen template service may race
# with cloud-init during boot causing issues with host key generation. This
# drop-in config adds a condition to sshd-keygen@.service if it exists and
# prevents the sshd-keygen units from running *if* cloud-init is going to run.
#
[Unit]
ConditionPathExists=!/run/systemd/generator.early/multi-user.target.wants/cloud-init.target
```

Note there are two systemd files listed above, sshd-keygen@.service from the sshd package and `disable-sshd-keygen-if-cloud-init-active.conf` file which comes from the cloud-init rpm

This is blocking the keygen and causing sshd to fail to start.

This can be fixed by either removing cloud-init or calling `/usr/libexec/openssh/sshd-keygen` manually.

I notice the upstream CI is using centos 9 and my overcloud nodes were deployed with centos 8, maybe this default just needs to be bumped.