Comment 3 for bug 1893697

Running the `octavia-diskimage-retrofit` tool manually on the unit using the QCOW2 image downloaded from glance reveals the following:

> update-initramfs: Generating /boot/initrd.img-5.4.0-45-generic
> W: plymouth module (/usr/lib/x86_64-linux-gnu/plymouth//.so) missing, skipping that theme.
> Processing triggers for linux-image-5.4.0-45-generic (5.4.0-45.49) ...
> /etc/kernel/postinst.d/dkms:
> * dkms: running auto installation service for kernel 5.4.0-45-generic
> ...done.
> /etc/kernel/postinst.d/initramfs-tools:
> update-initramfs: Generating /boot/initrd.img-5.4.0-45-generic
> W: plymouth module (/usr/lib/x86_64-linux-gnu/plymouth//.so) missing, skipping that theme.
> Error 24 : Write error : cannot write compressed block
> E: mkinitramfs failure cpio 141 lz4 -9 -l 24

The script in the snap does already grow the root filesystem to accommodate for upgraded packages:
https://github.com/openstack-charmers/octavia-diskimage-retrofit/blob/25cbc42fdefa50dc5cef0a55c1bd50dbcc74e0da/src/retrofit/retrofit.sh#L83

We may need to increase the headroom a bit.