s390x: kola testiso pxe-online-install.rootfs-appended fails

[nikita-dubrovskii]

Boot fails:

Mar 06 14:16:38 systemd[1]: Starting coreos-livepxe-rootfs.service - Acquire Live PXE rootfs Image...
Mar 06 14:16:39 coreos-livepxe-rootfs[835]: No rootfs image found.  Modify your PXE configuration to add the rootfs
Mar 06 14:16:39 coreos-livepxe-rootfs[835]: image as a second initrd, or use the coreos.live.rootfs_url kernel parameter
Mar 06 14:16:39 coreos-livepxe-rootfs[835]: to specify an HTTP or HTTPS URL to the rootfs.
Mar 06 14:16:39 systemd[1]: coreos-livepxe-rootfs.service: Main process exited, code=exited, status=1/FAILURE

Despite concatenated coreos-live-initramfs contains all required files withing:

89684928      0x5587BC0       ASCII cpio archive (SVR4 with no CRC), file name: "root.squashfs", file name length: "0x0000000E", file size: "0x26C4C000"                                                                                                                                                                      
740113468     0x2C1D3C3C      ASCII cpio archive (SVR4 with no CRC), file name: "etc", file name length: "0x00000004", file size: "0x00000000"                                                                                                                                                                                
740113584     0x2C1D3CB0      ASCII cpio archive (SVR4 with no CRC), file name: "etc/coreos-live-rootfs", file name length: "0x00000017", file size: "0x00000012" 

Those are not present under /