Vagrant VM provisioning doesn't have any mechanism for user interaction.
For this reason, it is necessary to tell APT that we are in a
non-interactive session and any install question should be answered
automatically by its preset.
For this reason, according to issue #42 and GitHub PR #43, I propose to
add "quiet" option to install.sh. This option tells Debian-based systems
to run APT in non-interactive mode. In case of important questions
during install, we can update the preset list specified in quiet_install
subroutine.
Flag functionality can always be extended in the future to support
unexpected cases where Vagrant provision hangs due to user interaction
request by some other program.
Change-Id: Iab3ce5f9b19cd6bfcf2fa180c433fb5d5d521914
