lxc: create /lxc directory by default

The containers are stored in /lxc rather then in /var/lib/lxc. The latter is
not suitable for OpenWrt.

Signed-off-by: Luka Perkov <luka@openwrt.org>

utils/lxc/Makefile

 	$(CP) \
 		$(PKG_INSTALL_DIR)/etc/lxc/default.conf \
 		$(1)/etc/lxc/lxc.conf
+
+	$(INSTALL_DIR) $(1)/lxc/
 endef
 
 define Package/lxc-hooks/install