Try to validate that module-data is working

`bind::defaults::supported` should always have a boolean value. If it does not,
then this means either 1) user error (e.g. the user defined some other value
for the key) or 2) module_data is not functioning correctly.

manifests/defaults.pp

@@ -13,6 +13,9 @@ class bind::defaults (
     $nsupdate_package       = undef,
     $managed_keys_directory = undef,
 ) {
+    unless is_bool($supported) {
+        fail('Please ensure that the dependencies of the bind module are installed and working correctly')
+    }
     unless $supported {
         fail('Platform is not supported')
     }