Additional LKM not added after upgrading to Ubuntu 18.04 (maybe be a bug in "libkmod")

Hi, I have reported on Dracut GitHub the following issue https://github.com/dracutdevs/dracut/issues/426 .

After upgrading to Ubuntu 18.04 (Linuxmint 19) dracut does not add additional drivers.

After a lot of investigation I found a problem into the libkmod.

---------------------------------------------
Here is a sample code to replicate the issue:
---------------------------------------------

#include <libkmod.h>
#include <stdio.h>

#define _cleanup_(x) __attribute__((cleanup(x)))

static inline void kmod_module_unref_listp(struct kmod_list **p) {
        if (*p)
                kmod_module_unref_list(*p);
}

#define _cleanup_kmod_module_unref_list_ _cleanup_(kmod_module_unref_listp)

static inline void kmod_module_info_free_listp(struct kmod_list **p) {
        if (*p)
                kmod_module_info_free_list(*p);
}

#define _cleanup_kmod_module_info_free_list_ _cleanup_(kmod_module_info_free_listp)

static inline void kmod_unrefp(struct kmod_ctx **p) {
        kmod_unref(*p);
}

#define _cleanup_kmod_unref_ _cleanup_(kmod_unrefp)

int main(int argc, char** argv) {
    _cleanup_kmod_unref_ struct kmod_ctx *ctx = NULL;
    _cleanup_kmod_module_unref_list_ struct kmod_list *list = NULL;
    int err;

    //char alias[2048] = "cryptd";
    char alias[2048] = "ahci cryptd";

    char kerneldir[256] = "/lib/modules/4.15.0-24-generic/";

    printf("libkmod tester...\n");

    ctx = kmod_new(kerneldir, NULL);
    err = kmod_module_new_from_lookup(ctx, alias, &list);

    if (err < 0) {
        printf("Error (%d) looking for aliases \"%s\"\n.", err, alias);
        return 1;
    }

    printf("Got list pointer 0x%lx .\n.", (unsigned long)(void *)list);

    return 0;
}

----------------------------------------
And here the script to build and run it:
----------------------------------------

#!/bin/bash

CUR_DIR=$(dirname $0)
EXE_NAME=kmod-tester

gcc -Wall *.c -lkmod -o ${EXE_NAME} && \
${CUR_DIR}/${EXE_NAME}

Regards,
Antonio Petricca

---------------
lsb_release -rd
---------------

Description: Linux Mint 19 Tara
Release: 19

-------------------------
apt-cache policy libkmod2
-------------------------

libkmod2:
  Installed: 24-1ubuntu3
  Candidate: 24-1ubuntu3
  Version table:
 *** 24-1ubuntu3 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        100 /var/lib/dpkg/status