lvmetad not available during system boot

[Tsvetomir Dimitrov]

I have got a clean Ubuntu 18.04 install with LUKS full disk encryption and I experience slow boot time compared to Ubuntu 16.04 and 17.10. What exactly happends:
1. Power up the laptop.
2. The OS loads and prompts for device password
3. Nothing happens for 2 or 3 iterations of the progress bar (the moving dots).
4. The OS boots and login screen is presented.

What I feel wrong and it didn't happen neither on 16.04 nor on 17.10 is the delay at step 3.

In /var/log/boot.log I noticed these lines:

  WARNING: Failed to connect to lvmetad. Falling back to device scanning.
  Volume group "ubuntu-vg" not found
  Cannot process volume group ubuntu-vg
  WARNING: Failed to connect to lvmetad. Falling back to device scanning.
  Reading all physical volumes. This may take a while...
  Found volume group "ubuntu-vg" using metadata type lvm2
  WARNING: Failed to connect to lvmetad. Falling back to device scanning.
  3 logical volume(s) in volume group "ubuntu-vg" now active

I managed to reproduce the same issue on a VM with standard installation by selecting "Encrypt the new Ubuntu installation for security".

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: systemd 237-3ubuntu10
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sun May 6 17:23:41 2018
MachineType: LENOVO 20C500F8BM
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-20-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash vt.handoff=1
SourcePackage: systemd
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/23/2016
dmi.bios.vendor: LENOVO
dmi.bios.version: J9ET9EWW (2.24 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20C500F8BM
dmi.board.vendor: LENOVO
dmi.board.version: SDK0E50510 PRO
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrJ9ET9EWW(2.24):bd09/23/2016:svnLENOVO:pn20C500F8BM:pvrThinkPadEdgeE440:rvnLENOVO:rn20C500F8BM:rvrSDK0E50510PRO:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.family: ThinkPad Edge E440
dmi.product.name: 20C500F8BM
dmi.product.version: ThinkPad Edge E440
dmi.sys.vendor: LENOVO