60 second hang during shutdown

[Colin Law]

On up to date Yaketty I intermittently see a 60 second hang on shutdown. In attached logs the hang was at Aug 08 09:58:25

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: systemd 231-1
ProcVersionSignature: Ubuntu 4.4.0-33.52-generic 4.4.15
Uname: Linux 4.4.0-33-generic x86_64
ApportVersion: 2.20.3-0ubuntu5
Architecture: amd64
CurrentDesktop: Unity
Date: Mon Aug 8 10:10:31 2016
InstallationDate: Installed on 2016-08-02 (5 days ago)
InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Alpha amd64 (20160802)
MachineType: Hewlett-Packard Presario CQ57 Notebook PC
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-33-generic root=UUID=aaca48e9-0f14-4b6b-ad60-fe93989c14b8 ro quiet splash vt.handoff=7
SourcePackage: systemd
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/17/2011
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: F.47
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: 3577
dmi.board.vendor: Hewlett-Packard
dmi.board.version: 24.49
dmi.chassis.asset.tag: Chassis Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: Hewlett-Packard
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnHewlett-Packard:bvrF.47:bd12/17/2011:svnHewlett-Packard:pnPresarioCQ57NotebookPC:pvr068E120000204910000620100:rvnHewlett-Packard:rn3577:rvr24.49:cvnHewlett-Packard:ct10:cvrChassisVersion:
dmi.product.name: Presario CQ57 Notebook PC
dmi.product.version: 068E120000204910000620100
dmi.sys.vendor: Hewlett-Packard