(maint) Fix curl install on ubuntu 1804

Because of the install command from https://github.com/puppetlabs/vanagon/blob/master/lib/vanagon/platform/deb.rb#L102 and a new version of curl we end up with an interctive message:

There are services installed on your system which need to be restarted when
certain libraries, such as libpam, libc, and libssl, are upgraded. Since these
restarts may cause interruptions of service for the system, you will normally be
prompted on each upgrade for the list of services you wish to restart.  You can
choose this option to avoid being prompted; instead, all necessary restarts will
be done for you automatically so you can avoid being asked questions on each
library upgrade.

Restart services during package upgrades without asking? [yes/no]

This commits adds DEBIAN_FRONTEND=noninteractive before any other install commands are run on the VM, to unblock the building of bolt until a new version of vanagon is released.

PORTED FROM: https://github.com/puppetlabs/puppet-agent/pull/1789

puppetlabs / bolt-vanagon

(maint) Fix curl install on ubuntu 1804 #117