Update default dex_uri value (#111)

Fixes #110

Author: treydock

manifests/init.pp

@@ -299,7 +299,7 @@
   Hash $oidc_settings = {},
 
   # Dex configs
-  Optional[String[1]] $dex_uri = undef,
+  Variant[String[1],Boolean] $dex_uri = '/dex',
   Openondemand::Dex_config $dex_config = {},
 
   # Misc configs