adding comments and removing random access spaces

mininet/link.py

@@ -122,6 +122,7 @@ class Intf( object ):
         "Return whether interface is up"
         if setUp:
             cmdOutput = self.ifconfig( 'up' )
+            # no output indicates success
             if cmdOutput:
                 error( "Error setting %s up: %s " % ( self.name, cmdOutput ) )
                 return False

mininet/util.py

@@ -192,6 +192,8 @@ def moveIntfNoRetry( intf, dstNode, srcNode=None, printError=False ):
         cmdOutput = srcNode.cmd( cmd )
     else:
         cmdOutput = quietRun( cmd )
+    # If ip link set does not produce any output, then we can assume
+    # that the link has been moved successfully.
     if cmdOutput:
         if printError:
             error( '*** Error: moveIntf: ' + intf +