[grid] Allowing -1 as port to use a random port

Fixes #9940

Author: diemol

java/src/org/openqa/selenium/grid/server/BaseServerOptions.java

@@ -41,7 +41,6 @@ public class BaseServerOptions {
 
   private static final Logger LOG = Logger.getLogger(BaseServerOptions.class.getName());
   private final Config config;
-  private int port = -1;
 
   public BaseServerOptions(Config config) {
     this.config = config;
@@ -54,17 +53,14 @@ public Optional<String> getHostname() {
 
   @ManagedAttribute(name = "Port")
   public int getPort() {
+    int port = config.getInt(SERVER_SECTION, "port")
+      .orElseGet(PortProber::findFreePort);
     if (port == -1) {
-      int newPort = config.getInt(SERVER_SECTION, "port")
-        .orElseGet(PortProber::findFreePort);
-
-      if (newPort < 0) {
-        throw new ConfigException("Port cannot be less than 0: " + newPort);
-      }
-
-      port = newPort;
+      return PortProber.findFreePort();
+    }
+    if (port < 0) {
+      throw new ConfigException("Port cannot be less than 0: " + port);
     }
-
     return port;
   }