Update instructions for custom image creation. a) Ubuntu xenial should be fine, b) different install of dib

DeployOpenStackHeat.md

@@ -32,7 +32,7 @@ Since generic OpenStack clouds do not support transporting SCTP packets over Flo
 To create an os-*-config ready Ubuntu image you could use the following commands:
 
 ```
-sudo apt-get install pip
+sudo apt-get install python-pip
 sudo pip installl virtualenv
 virtualenv ~/dib-virtualenv
 . ~/dib-virtualenv/bin/activate