Description of problem:

[root@rhel7b ~]# lsmod |grep l2tp
[root@rhel7b ~]# ip l2tp show tunnel

[waiting 10+ seconds, then hit ctrl-c]

[root@rhel7b ~]# lsmod |grep l2tp
l2tp_netlink           17851  0 
l2tp_core              34577  1 l2tp_netlink
[root@rhel7b ~]# ip l2tp show tunnel
[root@rhel7b ~]# 

It seems there is also no way of disabling modprobing while listing, the equivalent to iptables --modprobe=/dev/null/  So we have to depend on /sys entries to determine if the module is loaded before running ip l2tp show.