trailing semicolons on Config items that are semicolon separated create invalid bind config

[Adam Dyess]

juju config designate-bind forwarders="8.8.8.8;8.8.4.4;"
juju config designate-bind allowed_nets="192.168.0.0/24;192.168.0.0/24;"
juju config designate-bind allowed_recursion_nets="192.168.0.0/24;192.168.0.0/24;"

Generates invalid config in /etc/bind/named.conf.options

Please split the juju config options with ';' before applying to the config template. Or provide some way for the juju user to detect their mis-configuration without using juju run or juju ssh