fixed missing default value quotes for env.get calls in ejabberd.yml.tpl
fixed missing default value quotes for env.get calls in ejabberd.yml.tpl

The lookup call for the environment variables for
EJABBERD_MOD_ADMIN_EXTRA and EJABBERD_MOD_VERSION are missing quotes
for the default value. They are evaluated to false, while they look like
they would evaluate to true.

rroemhild/docker-ejabberd