Debian – How to resume or abandon an apt-get dist-upgrade after connection reset

In the middle of a "sudo apt-get dist-upgrade" on my Raspberry Pi, while waiting for user input, my ssh connection got reset. I was not running in a screen. The last few lines looked like this:

Installing new version of config file /etc/init.d/procps ...

Configuration file '/etc/sysctl.conf'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
   What would you like to do about it ?  Your options are:
    Y or I  : install the package maintainer's version
    N or O  : keep your currently-installed version
      D     : show the differences between the versions
      Z     : start a shell to examine the situation
 The default action is to keep your current version.
*** sysctl.conf (Y/I/N/O/D/Z) [default=N] ? Connection reset by <ip>

"ps" still shows the old apt-get process running…

$ ps -aux | grep apt
root      2375  0.0  0.3   6008  1636 ?        S    03:03   0:00 sudo apt-get dist-upgrade
root      2376  0.0  6.2  33428 27872 ?        S    03:03   0:18 apt-get dist-upgrade

I've got 1.1G in /var/cache/apt/archives, and can't successfully try a new attempt to apt-get dist-upgrade.

$ sudo apt-get dist-upgrade
E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)
E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?

What should I do now? Any way to resume the dist-upgrade in progress? If not, what's a good way to back out and try again?