install does not trigger initramfs update

[Scott Moser]

installing open-iscsi provides some initramfs hooks, but does not update the initramfs.
the result is:
  apt-get install open-iscsi
  reboot

will not allow you to use iscsi in initramfs.

per discussion just now in ubuntu-devel it should call update-initramfs -u in postinst [1]

--
[1] http://irclogs.ubuntu.com/2015/06/19/%23ubuntu-devel.html#t18:04

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: open-iscsi 2.0.873-3ubuntu11
ProcVersionSignature: User Name 3.19.0-21.21-generic 3.19.8
Uname: Linux 3.19.0-21-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
Date: Fri Jun 19 18:12:32 2015
Ec2AMI: ami-00000422
Ec2AMIManifest: FIXME
Ec2AvailabilityZone: nova
Ec2InstanceType: m1.small
Ec2Kernel: aki-00000002
Ec2Ramdisk: ari-00000002
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: open-iscsi
UpgradeStatus: No upgrade log present (probably fresh install)