dracut-reencrypt: call "udevadm settle" once more

Closed username-removed-1275695 requested to merge haraldh/cryptsetup:settle into master

Somehow testing in qemu resulted sometimes in an endless loop. Either the timing or the settle fixed the issue. When the VM was in an endless loop, an strace showed, that the first 512 and 1024 of the crypt partition was read over and over. Either it was the udev blkid, or some device mapper udev rule. Maybe the reencrypt tool opens and closes the device fd, where the close triggers a udev blkid and causes the reencrypt tool to reread the device... Anyhow.. with this settle the issue was not seen anymore.