Handle waiting for dpkg lock

[grosscol]

Ubuntu's unattended updates will lock dpkg when the system comes up for the first time. This will cause the ansible role that installs packages to fail with "waiting for /var/lib/dpkg/lock-frontend".

Could try adapting solutions from:

• https://joelvasallo.com/packer-ansible-unable-to-acquire-dpkg-lock-c7eb5863127d
• https://stackoverflow.com/a/49221148
• apt upgrade full raises a "Could not get lock /var/lib/dpkg/lock-frontend" ansible/ansible#51663

The interim way of dealing with this is to just wait to run ansible until the unattended upgrades finishes.