execute: don't fail child when we don't have privileges to setup namespaces

If we don't have privileges to setup the namespaces then we are most likely
running inside some sort of unprivileged container, hence not being able to
create namespace is not a problem because spawned service can't access host
system anyway.

src/core/execute.c

@@ -1545,7 +1545,10 @@ static int exec_child(ExecCommand *command,
                                 context->protect_home,
                                 context->protect_system,
                                 context->mount_flags);
-                if (err < 0) {
+
+                if (err == -EPERM)
+                        log_error_unit(params->unit_id, "Failed to setup namespace, ignoring: %s", strerror(-err));
+                else if (err < 0) {
                         *error = EXIT_NAMESPACE;
                         return err;
                 }