updated container detection to new lxc (#17063)

fixes #17030

lib/ansible/module_utils/facts.py

@@ -2877,6 +2877,7 @@ class LinuxVirtual(Virtual):
 
     # For more information, check: http://people.redhat.com/~rjones/virt-what/
     def get_virtual_facts(self):
+        # old lxc/docker
         if os.path.exists('/proc/1/cgroup'):
             for line in get_file_lines('/proc/1/cgroup'):
                 if re.search(r'/docker(/|-[0-9a-f]+\.scope)', line):
@@ -2888,6 +2889,14 @@ class LinuxVirtual(Virtual):
                     self.facts['virtualization_role'] = 'guest'
                     return
 
+        # newer lxc does not appear in cgroups anymore but sets 'container=lxc' environment var
+        if os.path.exists('/proc/1/environ'):
+            for line in get_file_lines('/proc/1/environ'):
+                if re.search('container=lxc', line):
+                    self.facts['virtualization_type'] = 'lxc'
+                    self.facts['virtualization_role'] = 'guest'
+                    return
+
         if os.path.exists('/proc/vz'):
             self.facts['virtualization_type'] = 'openvz'
             if os.path.exists('/proc/bc'):