launch_daemon: fix check for existing directory

BEntry.InitCheck returns B_OK even if the leaf does not exist. So the
code in launch daemon to create directories (/tmp and
/var/shared_memory) was never run.

Fixes #12760.

src/servers/launch/AbstractEmptyDirectoryJob.cpp

@@ -23,7 +23,7 @@ status_t
 AbstractEmptyDirectoryJob::CreateAndEmpty(const char* path) const
 {
 	BEntry entry(path);
-	if (entry.InitCheck() != B_OK) {
+	if (!entry.Exists()) {
 		create_directory(path, 0777);
 
 		status_t status = entry.SetTo(path);