Some services look for /etc/timezone on Debian/Ubuntu, so we should
introduce it to the containers.
In addition, added prechecks for /etc/localtime and /etc/timezone.
Closes-Bug: #1821592
Change-Id: I9fef14643d1bcc7eee9547eb87fa1fb436d8a6b3
(cherry picked from commit 4b5df0d8660543230a48d279f508c3205c8fc406)