Workaround for cgdelete deleting cgroup but returning error

fixes #513

mininet/node.py

@@ -681,7 +681,9 @@ class CPULimitedHost( Host ):
         "Clean up our cgroup"
         # info( '*** deleting cgroup', self.cgroup, '\n' )
         _out, _err, exitcode = errRun( 'cgdelete -r ' + self.cgroup )
-        return exitcode == 0  # success condition
+        # Sometimes cgdelete returns a resource busy error but still
+        # deletes the group; next attempt will give "no such file"
+        return exitcode == 0  or ( 'no such file' in _err.lower() )
 
     def popen( self, *args, **kwargs ):
         """Return a Popen() object in node's namespace
@@ -703,7 +705,7 @@ class CPULimitedHost( Host ):
     def cleanup( self ):
         "Clean up Node, then clean up our cgroup"
         super( CPULimitedHost, self ).cleanup()
-        retry( retries=3, delaySecs=1, fn=self.cgroupDel )
+        retry( retries=3, delaySecs=.1, fn=self.cgroupDel )
 
     _rtGroupSched = False   # internal class var: Is CONFIG_RT_GROUP_SCHED set?