apt-get/dpkg interruption checker

# Background

Ubuntu ships with a tool called `unattended-upgrade` which periodically installs security patches. However, we've observed some cases where auto-upgrade can stop on some machines. One of the reason is that last upgrade was aborted, leaving `dpkg` in an intermediate state. It requires human interaction to fix such state.

# Design

* Check `dpkg` locks to see if it's held for too long.
* Check `apt-get`/`dpkg` logs for last failure details.