fix(dracut-functions.sh): get block device driver if in a virtual subsystem

fix(dracut-functions.sh): get block device driver if in a virtual subsystem

dracut does not install the kernel module of the block device that contains
the root filesystem if the following preconditions are met:
- Running in host-only mode.
- Symlinks of all block devices needed to boot the system pointing to virtual
subsystems.

The get_dev_module function uses "udevadm info -a" to get the corresponding
kernel modules of a /sys/class/*/* or /dev/* device. This function is called
in modules.d/90kernel-modules/module-setup.sh to detect if dracut must install
block device drivers in host-only mode. The symlinks in /sys/dev/block/
usually point to "real" devices in /sys/devices/pci*. But, we have come across
some NVMe systems where the kernel creates the symlinks in /sys/dev/block/
pointing to "virtual" devices instead. In this case, udevadm never finds any
"driver" attributes following up the chain of parent devices.