fix(auth-process): use canonicalized hostname in client init

lib/auth_processes/mongodb.js

@@ -9,17 +9,14 @@ class MongoAuthProcess {
     this.port = port;
 
     // Set up service name
-    serviceName = serviceName || options.gssapiServiceName || 'mongodb';
+    this.serviceName = serviceName || options.gssapiServiceName || 'mongodb';
 
     // Options
     this.canonicalizeHostName =
       typeof options.gssapiCanonicalizeHostName === 'boolean'
         ? options.gssapiCanonicalizeHostName
         : false;
 
-    this.service =
-      process.platform === 'win32' ? `${serviceName}/${host}` : `${serviceName}@${host}`;
-
     // Set up first transition
     this._transition = firstTransition(this);
 
@@ -58,7 +55,12 @@ class MongoAuthProcess {
         Object.assign(initOptions, { user: username, password });
       }
 
-      kerberos.initializeClient(self.service, initOptions, (err, client) => {
+      const service =
+        process.platform === 'win32'
+          ? `${this.serviceName}/${this.host}`
+          : `${this.serviceName}@${this.host}`;
+
+      kerberos.initializeClient(service, initOptions, (err, client) => {
         if (err) return callback(err, null);
 
         self.client = client;