setting up sql_connection in nova.conf, it was missing for ubuntu impacting icehouse where we use stock nova packages. On havana it would be no-op as it is already present in locally build nova package

Change-Id: I13cd6de088f2d8a6e68f69ac7f9fca15aaff0f26
Merge "setting up sql_connection in nova.conf, it was missing for ubuntu impacting icehouse where we use stock nova packages. On havana it would be no-op as it is already present in locally build nova package"