oauth2: fix token expires time not updated (#3455)

Signed-off-by: Jeff Luo <[email protected]>

Author: JeffLuoo

src/flb_oauth2.c

@@ -390,6 +390,8 @@ char *flb_oauth2_token_get(struct flb_oauth2 *ctx)
             flb_info("[oauth2] access token from '%s:%s' retrieved",
                      ctx->host, ctx->port);
             flb_http_client_destroy(c);
+            ctx->issued = time(NULL);
+            ctx->expires = ctx->issued + ctx->expires_in;
             return ctx->access_token;
         }
     }