[docker] parse subsystem

Author: sjenriquez

utils/dockerutil.py

@@ -334,12 +334,17 @@ def _tags_match_patterns(self, tags, filters):
                     return True
         return False
 
+    @classmethod
+    def _parse_subsystem(cls, line):
+        i = line[2].rfind('docker')
+        return line[2][i:]
+
     @classmethod
     def find_cgroup_from_proc(cls, mountpoints, pid, subsys, docker_root='/'):
         proc_path = os.path.join(docker_root, 'proc', str(pid), 'cgroup')
         with open(proc_path, 'r') as fp:
             lines = map(lambda x: x.split(':'), fp.read().splitlines())
-            subsystems = dict(zip(map(lambda x: x[1], lines), map(lambda x: x[2] if x[2][0] != '/' else x[2][1:], lines)))
+            subsystems = dict(zip(map(lambda x: x[1], lines), map(cls._parse_subsystem, lines)))
 
         if subsys not in subsystems and subsys == 'cpuacct':
             for form in "{},cpu", "cpu,{}":