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>

configure.ac

@@ -96,6 +96,7 @@ AC_PLUGIN([hotplug],       [yes], [Setup and start udev or mdev hotplug daemon])
 AC_PLUGIN([rtc],           [yes], [Save and restore RTC using hwclock])
 AC_PLUGIN([tty],           [yes], [Automatically activate new TTYs, e.g. USB-to-serial])
 AC_PLUGIN([urandom],       [yes], [Setup and save random seed at boot/shutdown])
+AC_PLUGIN([testserv],      [no],  [Test plugin to start test serv daemon])
 
 # Check for extra arguments or packages
 AC_ARG_WITH(fstab,