KVM: selftests: Use perf_test_destroy_vm in memslot_modification_stress_test

Change memslot_modification_stress_test to use perf_test_destroy_vm
instead of manually calling ucall_uninit and kvm_vm_free.

No functional change intended.
Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
Message-Id: <20211111001257.1446428-5-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/memslot_modification_stress_test.c

@@ -116,8 +116,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 	perf_test_join_vcpu_threads(nr_vcpus);
 	pr_info("All vCPU threads joined\n");
 
-	ucall_uninit(vm);
-	kvm_vm_free(vm);
+	perf_test_destroy_vm(vm);
 }
 
 static void help(char *name)