GUACAMOLE-641: Migrate existing extensions to singleton LocalEnvironment.

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleConnection.java

@@ -202,7 +202,7 @@ public class SimpleConnection extends AbstractConnection {
             throws GuacamoleException {
 
         // Retrieve proxy configuration from environment
-        Environment environment = new LocalEnvironment();
+        Environment environment = LocalEnvironment.getInstance();
         GuacamoleProxyConfiguration proxyConfig = environment.getDefaultGuacamoleProxyConfiguration();
 
         // Get guacd connection parameters