Dont go through authentication flow when we have token from the keychain

- but still see if he's not yet expired

Author: stigi

Sources/OAuth2Client/NXOAuth2Client.m

@@ -119,7 +119,11 @@ - (void)setAccessToken:(NXOAuth2AccessToken *)value;
 
 - (void)requestAccess;
 {
-	if (username != nil && password != nil) {	// username password flow
+	if (self.accessToken) {
+		if (self.accessToken.hasExpired){
+			[self refreshAccessToken];
+		}
+	} else if (username != nil && password != nil) {	// username password flow
 		[self requestTokenWithUsernameAndPassword];
 	} else {									// web server flow
 		NSAssert(redirectURL, @"Web server flow without redirectURL");