nginx_site now uses boolean values

The nginx_site parameters $enable and $install were using quoted boolean
which is not recommended.  This patch convert them to boolean defaults
(respectively false and true) and update the parent calls.  The
parameters are only used inside of nginx_site call, so no template needs
to be updated.

Also added trailing commas.

Change-Id: Ie70b24f606486ff3789cf7fd47b7faf9f222c708
Merge "nginx_site now uses boolean values" into production