image/ubuntu: suppress the packages' configuration dialogs
image/ubuntu: suppress the packages' configuration dialogs

make iso stops during creation of the Ubuntu chroot (intended for image
based provisioning) and displays packages' configuration dialogs
(in particular postfix). Force a non-interactive packages installation.
While at it suppress the warnings regarding an unsupported locale.

Closes-bug: #1403390
Related-bug: #1383641
blueprint support-ubuntu-trusty
Change-Id: I8c104a41d267e30feea72619ae4ad27b6d59a562

eayunstack/fuel-main,zhaochao/fuel-main,SmartInfrastructures/fuel-main-dev,ddepaoli3/fuel-main-dev,ddepaoli3/fuel-main-dev,Fiware/ops.Fuel-main-dev,AnselZhangGit/fuel-main,SergK/fuel-main,zhaochao/fuel-main,AnselZhangGit/fuel-main,AnselZhangGit/fuel-main,SergK/fuel-main,dancn/fuel-main-dev,huntxu/fuel-main,SergK/fuel-main,dancn/fuel-main-dev,Fiware/ops.Fuel-main-dev,eayunstack/fuel-main,stackforge/fuel-main,ddepaoli3/fuel-main-dev,teselkin/fuel-main,AnselZhangGit/fuel-main,eayunstack/fuel-main,ddepaoli3/fuel-main-dev,huntxu/fuel-main,teselkin/fuel-main,stackforge/fuel-main,zhaochao/fuel-main,teselkin/fuel-main,Fiware/ops.Fuel-main-dev,stackforge/fuel-main,SmartInfrastructures/fuel-main-dev,Fiware/ops.Fuel-main-dev,dancn/fuel-main-dev,huntxu/fuel-main,SmartInfrastructures/fuel-main-dev,zhaochao/fuel-main,teselkin/fuel-main,dancn/fuel-main-dev,SmartInfrastructures/fuel-main-dev,zhaochao/fuel-main