Remove ifupdown(eth0) connection

Open your file manager and go to /etc/network/. Once there, you have to edit the file interfaces like this:

  sudo gedit /etc/network/interfaces 

or

  gksu mousepad /etc/network/interfaces

and delete all entries in there except for auto lo / iface lo inet loopback.

The following lines

   auto lo
   iface lo inet loopback

have to be the only entries present in /etc/network/interfaces.

Next you should edit a second file located in /etc/NetworkManager/NetworkManager.conf. Use this code in a terminal window:

   sudo gedit /etc/NetworkManager/NetworkManager.conf

or

   gksu mousepad /etc/NetworkManager/NetworkManager.conf

Look for this entry [ifupdown] and edit the entry to look like this:

   [ifupdown]
   managed=false

Reboot and reconfigure if necessary your network using the network applet from system tray.

Open terminal and enable super user mode.

nano /etc/NetworkManager/NetworkManager.conf

The contents of the file will be like this:

[main]
plugins=ifupdown,keyfile,ofono
dns=dnsmasq  
[ifupdown]  
managed=true

Please change the plugins section to:

plugins=keyfile,ofono

Restart the network manager:

service network-manager restart

It worked for me, I hope it will work or you too.