network-manager 1.2.2 blocked reboot/shutdown process

[Alex Tu]

the reboot process is blocked by network-manager time out on current xenial network-manager 1.2.2, but passed on 1.2.4 which is on proposed ppa.

Please see attached photo which took for the timeout message shown on screen.

some more information of proposed network-manager
u@u-7920-Tower:~$ apt-cache policy network-manager
network-manager:
  Installed: 1.2.2-0ubuntu0.16.04.3
  Candidate: 1.2.4-0ubuntu0.16.04.1
  Version table:
     1.2.4-0ubuntu0.16.04.1 500
        500 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 Packages
 *** 1.2.2-0ubuntu0.16.04.3 500
        500 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.1.93-0ubuntu4 500
        500 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages

fix need landing LP: #1645698
fix required by: LP: #1655901