Introduce Virtuozzo distribution

Virtuozzo is a RHEL-based distribution serving as a platform OS
to host proprietary container virtualization
(formerly, Parallels Cloud Server).

We moved away from CloudLinux distribution, which has actually
no support in Devstack (no such clause in is_fedora).
As it was us who introduced CloudLinux, by this patch
we replace it with Virtuozzo distribution.

More info on Virtuozzo company here: http://virtuozzo.com

Change-Id: Ib8a77e4611ebc05bc0aa50bb83ab79c412e21c74
diff --git a/functions-common b/functions-common
index a26cc50..90217c9 100644
--- a/functions-common
+++ b/functions-common
@@ -380,7 +380,8 @@
         DISTRO="sle${os_RELEASE%.*}"
     elif [[ "$os_VENDOR" =~ (Red.*Hat) || \
         "$os_VENDOR" =~ (CentOS) || \
-        "$os_VENDOR" =~ (OracleLinux) ]]; then
+        "$os_VENDOR" =~ (OracleLinux) || \
+        "$os_VENDOR" =~ (Virtuozzo) ]]; then
         # Drop the . release as we assume it's compatible
         # XXX re-evaluate when we get RHEL10
         DISTRO="rhel${os_RELEASE::1}"
@@ -421,7 +422,7 @@
 
     [ "$os_VENDOR" = "Fedora" ] || [ "$os_VENDOR" = "Red Hat" ] || \
         [ "$os_VENDOR" = "CentOS" ] || [ "$os_VENDOR" = "OracleLinux" ] || \
-        [ "$os_VENDOR" = "CloudLinux" ] || [ "$os_VENDOR" = "kvmibm" ]
+        [ "$os_VENDOR" = "Virtuozzo" ] || [ "$os_VENDOR" = "kvmibm" ]
 }