Add plugin and test to reproduce failing tests since c9fe9af

With all the change and revert mess of the HOOK_BASEFS_UP tests started
failing due to usr.so and sys.so failed to set up their conditions.  It
then became clear that boomisc.so cleaned up /run ... with the revert
we got service_register() to be called before global_rlimit[] was setup
causing services registered by plugins, before conf_init(), to crash.

This plugin and test is here to ensure we catch this problem in case of
any future refactor.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

test/tenv/lib.sh

@@ -57,6 +57,11 @@ assert_restarts()
 	assert "Finit has registered restarts" "$(texec initctl status "$2" | awk '/Restarts/{print $3;}')" -ge "$1"
 }
 
+assert_norestart()
+{
+	assert "Service $1 is stable, no restarts" "$(texec initctl status "$1" | awk '/Restarts/{print $3;}')" -eq "0"
+}
+
 assert_desc()
 {
 	assert "Service description == $1" "$(texec initctl status "$2" | grep 'Description' | sed 's/Description : //')" = "$1"