Support RHEL 9

This patch includes changes required to run devstack on RHEL 9.

- en_US.utf8 is provided by glibc-langpack-en
- iptables command is provided by iptables-nft
- Use /etc/os-release to identify the distro in RHEL 9 as it doesn't
  provide lsb_release command.
- CRB repository name is different from CentOS 9

Change-Id: I8f6d9263b24f9c2cf82e09258e2d14d7766ad337
diff --git a/files/rpms/general b/files/rpms/general
index b6866de..8a5755c 100644
--- a/files/rpms/general
+++ b/files/rpms/general
@@ -6,9 +6,11 @@
 gcc-c++
 gettext  # used for compiling message catalogs
 git-core
+glibc-langpack-en # dist:rhel9
 graphviz # needed only for docs
 httpd
 httpd-devel
+iptables-nft # dist:rhel9
 iptables-services
 java-1.8.0-openjdk-headless
 libffi-devel