invoking "sudo systemctl start network-1manager.service" in systemd rescue shell causes it to be unresponsive

[Karl-Philipp Richter]

After a corruption of a btrfs mountpoint in `/etc/fstab` (not `/` or `/home/`) the `systemd` rescue shell was started. After invoking `sudo systemctl start network-manager.service`

    Error getting authority: Error initializing authority: Could not connect: No such file or directory (g-io-quark, 1)
    Hung up

was printed and the shell became unresponsive to keyboard input (only Ctrl+Alt+F[>1] changed to screens with blinking cursors; not even 7 Ctrl+Alt+Del within two seconds triggered reboot which normally happends in `systemd` rescue shell.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: systemd 225-1ubuntu9
Uname: Linux 4.3.3-040303-generic x86_64
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Jan 28 05:16:47 2016
InstallationDate: Installed on 2015-12-12 (46 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
MachineType: LENOVO 20221
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.3.3-040303-generic root=UUID=791b47e7-915d-4d5a-bce0-d7e9b660a2ab ro rootflags=subvol=ubuntu-main-root
SourcePackage: systemd
UdevLog: Error: [Errno 2] Datei oder Verzeichnis nicht gefunden: '/var/log/udev'
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/12/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: 71CN51WW(V1.21)
dmi.board.asset.tag: No Asset Tag
dmi.board.name: INVALID
dmi.board.vendor: LENOVO
dmi.board.version: 31900003WIN8 STD MLT
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Lenovo IdeaPad Z500 Touch
dmi.modalias: dmi:bvnLENOVO:bvr71CN51WW(V1.21):bd07/12/2013:svnLENOVO:pn20221:pvrLenovoIdeaPadZ500Touch:rvnLENOVO:rnINVALID:rvr31900003WIN8STDMLT:cvnLENOVO:ct10:cvrLenovoIdeaPadZ500Touch:
dmi.product.name: 20221
dmi.product.version: Lenovo IdeaPad Z500 Touch
dmi.sys.vendor: LENOVO

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.