Support CentOS Stream 9

This patch includes changes required to run devstack on CentOS Stream 9
which has been already published in official repos by CentOS team [1]:

- Add RDO deps repository for CS9.
- remove xinetd package from installation for swift. Note that
  rsync-daemon is installed which should work fine.
- Replace genisoimage by xorriso in CS9.
- Use /etc/os-release to identify the distro in CS9 as it doesn't
  provide lsb_release command.
- Use pip from rpm package instead of from get-pip.py as done in Fedora.
- Add non-voting job devstack-platform-centos-9-stream to the check
  pipeline.

Change-Id: Ic67cddabd5069211dc0611994b8b8360bcd61bef
diff --git a/files/rpms/nova b/files/rpms/nova
index 8ea8ccc..9522e57 100644
--- a/files/rpms/nova
+++ b/files/rpms/nova
@@ -3,7 +3,7 @@
 dnsmasq # for q-dhcp
 dnsmasq-utils # for dhcp_release
 ebtables
-genisoimage # required for config_drive
+genisoimage # not:rhel9 required for config_drive
 iptables
 iputils
 kernel-modules
@@ -13,3 +13,4 @@
 rabbitmq-server # NOPRIME
 sqlite
 sudo
+xorriso # not:rhel8