systemd-udev-settle.service hangs on fedora 28

Recently while playing around disk partitions on fedora 28 I have observed that boot times were painfully slow on my laptop, when investigated found the issue was due to an entry for non existent swap partition in fstab.

To fix the issue I recreated a swap file system and added below lines to fstab:

# /etc/fstab
UUID=de9a1c4f-997e-4d01-a6ce-8e97cb01ce8b /                       ext4    defaults        1 1
UUID=8b897b38-3d29-4953-a706-6327601d9252 /boot                   ext4    defaults        1 2
UUID=1af3802c-a391-4a6a-8380-9e330fc0eb7d none                     swap    defaults        0 0

Mount the disk partitions then reboot and check:

mount -a

Checking the boot time report:

systemd-analyze
Startup finished in 1.476s (kernel) + 2.365s (initrd) + 6.587s (userspace) = 10.430s