RpcServer: let system allocate vsock ports

This greatly improves stability with concurrent test execution

Bug: 285204695
Test: atest --host binder_sdk_test
Change-Id: Ib7b76df693288033e55fa27786bf6efb21d0ebf0
diff --git a/libs/binder/tests/binderRpcTestService.cpp b/libs/binder/tests/binderRpcTestService.cpp
index 28125f1..aef9464 100644
--- a/libs/binder/tests/binderRpcTestService.cpp
+++ b/libs/binder/tests/binderRpcTestService.cpp
@@ -143,8 +143,8 @@
             break;
         case SocketType::VSOCK:
             LOG_ALWAYS_FATAL_IF(OK !=
-                                        server->setupVsockServer(VMADDR_CID_LOCAL,
-                                                                 serverConfig.vsockPort),
+                                        server->setupVsockServer(VMADDR_CID_LOCAL, VMADDR_PORT_ANY,
+                                                                 &outPort),
                                 "Need `sudo modprobe vsock_loopback`?");
             break;
         case SocketType::INET: {