lxc-auto: step by 1 sec up to $max_timeout

lxc-auto: step by 1 sec up to $max_timeout

If the user defines a $max_timeout of 30, the service will wait 30 seconds
before it considers lxc-stop complete even though lxc-stop might actually
finish much sooner.  This introduces an unneeded delay.

This commit changes the behavior to check once per second to see when lxc-stop
actually stops doing so up to $max_timeout.  It also slightly simplifies the
code with logic to append the -t $max_timeout to the script.

Signed-off-by: John Audia <graysky@archlinux.us>
(cherry picked from commit 7984d2d74a2fd83f036310888ad7486bff655c5a)