how auto do-release-upgrade by special configuration

I use "do-release-upgrades" for upgrade ubuntu 14.04---16.04 。
In process,I have to choose some configurations.

  What do you want to do about modified configuration file 50uattended-upgrades?
                           install the package maintainer's version
                           keep the local version currently installed
                           ..................................

I want to upgrade with no prompts，so I use "do-release-upgrades -d -f DistUpgradeViewNonInteractive".
It works,upgrade with nonInteractive.
But,I want choose the "install the ..........." not the default value "keep the local..........".

So, I use debconf-set-selections
"ucf ucf/changeprompt select install_new"
"unattended-upgrades unattended-upgrades/enable_auto_updates boolean true"
But,it don't works.

How can I solve this question?