REGTEST: add missing lua requirements on server removal test

The test that removes server via CLI is using LUA to check that servers
referenced in a LUA script cannot be removed. This requires LUA support
to be built in haproxy.

Split the test and create a new one containing only the LUA relevant
test. Mark it as LUA dependant.
diff --git a/reg-tests/server/cli_delete_server_lua.vtc b/reg-tests/server/cli_delete_server_lua.vtc
new file mode 100644
index 0000000..ab4200f
--- /dev/null
+++ b/reg-tests/server/cli_delete_server_lua.vtc
@@ -0,0 +1,44 @@
+# This script is to check that servers that are referenced by a lua script
+# cannot be removed at runtime.
+varnishtest "Delete lua server via cli"
+
+feature ignore_unknown_macro
+
+#REQUIRE_VERSION=2.5
+#REQUIRE_OPTIONS=LUA
+
+server s1 {
+	rxreq
+	txresp
+} -start
+
+haproxy h1 -conf {
+	global
+		lua-load ${testdir}/get_srv_stats.lua
+
+	defaults
+		mode http
+		timeout connect 1s
+		timeout client  1s
+		timeout server  1s
+
+	frontend fe
+		bind "fd@${feS}"
+		default_backend test
+
+	backend test
+		http-request add-header s1-stats %[lua.get_srv_stats(s1)]
+		server s1 ${s1_addr}:${s1_port}          # referenced in lua script
+} -start
+
+# make a request to force the execution of the lua script which references a
+# server
+client c1 -connect ${h1_feS_sock} {
+	txreq
+	rxresp
+} -run
+
+haproxy h1 -cli {
+	send "experimental-mode on; del server test/s1"
+	expect ~ "This server cannot be removed at runtime due to other configuration elements pointing to it."
+}