Set mkisofs_cmd to mkisofs in default config

CS10 EDPM job watcher tempest tests fails while creating server with
`No such file or directory: 'genisoimage'`.

mkisofs_cmd config option sets the genisoimage, is default in the nova
config.

In RHEL-10, we use xorriso package not genisoimage. mkisofs is used in
Nova conf[1]. We need to set the same in nova config so that instances
gets created.

https://gitlab.com/redhat/centos-stream/rpms/libisoburn/-/commit/e3a52310e179718055699d1845a2dec936d1ee16
provides mkisofs and genisoimage, Both of them are symlink for xorriso.

Currently we are going to use mkisofs as xorriso command does not found
in the nova-compute container based on [2].

Jira: OSPRH-16715

Links:
[1]. rdo-packages/nova-distgit@702f2fb
[2]. #971 (comment)

Signed-off-by: Chandan Kumar (raukadah) <raukadah@gmail.com>

Author: raukadah

templates/nova.conf

@@ -30,6 +30,7 @@ initial_ram_allocation_ratio=1.0
 initial_disk_allocation_ratio=0.9
 {{/*using a config drive will void issues with ovn and metadata*/}}
 force_config_drive=True
+mkisofs_cmd=/usr/bin/mkisofs
 {{end}}
 {{ if (index . "transport_url") }}
 transport_url={{.transport_url}}