BUG/MINOR: lua: Some lua init operation are processed unsafe

Operation luaL_openlibs() and lua_prepend path are processed whithout
the safe context, so in case of failure Haproxy aborts or stops without
error message.

This patch could be backported until 1.8
diff --git a/src/hlua.c b/src/hlua.c
index e1c316b..43a9745 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -8221,6 +8221,16 @@
 	 * process of HAProxy, this abort() is tolerated.
 	 */
 
+	/* Set safe environment for the initialisation. */
+	if (!SET_SAFE_LJMP(gL.T)) {
+		if (lua_type(gL.T, -1) == LUA_TSTRING)
+			error_msg = lua_tostring(gL.T, -1);
+		else
+			error_msg = "critical error";
+		fprintf(stderr, "Lua init: %s.\n", error_msg);
+		exit(1);
+	}
+
 	/* Initialise lua. */
 	luaL_openlibs(gL.T);
 #define HLUA_PREPEND_PATH_TOSTRING1(x) #x
@@ -8234,16 +8244,6 @@
 #undef HLUA_PREPEND_PATH_TOSTRING
 #undef HLUA_PREPEND_PATH_TOSTRING1
 
-	/* Set safe environment for the initialisation. */
-	if (!SET_SAFE_LJMP(gL.T)) {
-		if (lua_type(gL.T, -1) == LUA_TSTRING)
-			error_msg = lua_tostring(gL.T, -1);
-		else
-			error_msg = "critical error";
-		fprintf(stderr, "Lua init: %s.\n", error_msg);
-		exit(1);
-	}
-
 	/*
 	 *
 	 * Create "core" object.