Added scancode for backslash
Prevent endless loop in send_keys_to_vm

This happens if command is something like:
    command => "perl -i -0777 -pe 's/#\[community-testing\]\n#Include/[community-testing]\nInclude/s' /etc/pacman.conf",

The newline string (\n) is actually interpolated to a newline character (because "..." is used).

The while loop would never finish.

The command should look something like this (note the \\):
    command => "perl -i -0777 -pe 's/#\\[community-testing\\]\\n#Include/[community-testing]\\nInclude/s' /etc/pacman.conf",
Modifying pacman.conf to active testing repositories

Thanks to http://unix.stackexchange.com/a/26289 for pointing out I have to use -0777 in order to read the whole file at once. Without -0777, perl just reads one line at a time, making /s useless and let the substitution regex "fail".
Updating using pacman, rebooting, and some more tests

At this stage of the script, the Arch Linux VM is automatically updated to packages from the testing repositories.
After that, a reboot is initiated to demonstrate that the VM is booted using testing packages without errors.
Show info message after sleep
Print a "program ends" message

Reduced sleep time so the script ends faster.