node shell: remove unnecessary -m and unset HISTFILE

Since we already disable job notification with +m, it doesn't
make sense to set it in the original invocation!

It's also annoying if all of the host commands end up overwriting
your regular bash_history!!

mininet/node.py

@@ -125,11 +125,11 @@ class Node( object ):
         opts = '-cd' if mnopts is None else mnopts
         if self.inNamespace:
             opts += 'n'
-        # bash -m: enable job control, i: force interactive
+        # bash -i: force interactive
         # -s: pass $* to shell, and make process easy to find in ps
         # prompt is set to sentinel chr( 127 )
         cmd = [ 'mnexec', opts, 'env', 'PS1=' + chr( 127 ),
-                'bash', '--norc', '-mis', 'mininet:' + self.name ]
+                'bash', '--norc', '-is', 'mininet:' + self.name ]
         # Spawn a shell subprocess in a pseudo-tty, to disable buffering
         # in the subprocess and insulate it from signals (e.g. SIGINT)
         # received by the parent
@@ -157,7 +157,8 @@ class Node( object ):
                 break
             self.pollOut.poll()
         self.waiting = False
-        self.cmd( 'stty -echo; set +m' )
+        # +m: disable job control notification
+        self.cmd( 'unset HISTFILE; stty -echo; set +m' )
 
     def mountPrivateDirs( self ):
         "mount private directories"