update initramfs when installing plymouth theme

[Tim]

for encrypted installs, plymouth gets installed into initramfs, so updates to that should be calling 'update-initramfs -u' from the postinit script

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: ubuntu-gnome-default-settings 15.10.3
ProcVersionSignature: Ubuntu 4.2.0-7.7-generic 4.2.0
Uname: Linux 4.2.0-7-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.18-0ubuntu9
Architecture: amd64
CurrentDesktop: GNOME
Date: Thu Sep 10 19:11:33 2015
InstallationDate: Installed on 2012-09-23 (1082 days ago)
InstallationMedia: Ubuntu GNOME Remix 12.10 "Quantal Quetzal" - Alpha amd64(20120922)
PackageArchitecture: all
SourcePackage: ubuntu-gnome-default-settings
UpgradeStatus: No upgrade log present (probably fresh install)

[Bruce Pieterse (octoquad)]

Unable to reproduce.

[Tim (darkxst)]

closing seems like this was caused by broken upgrades