Handle errors if run_full_install fails in preflight updater

[eloquence]

The run_full_install method currently runs check_call as follows:

    sdlog.info("Running sdw-admin apply")
    cmd = ["sdw-admin", "--apply"]
    subprocess.check_call(cmd)

We don't catch CalledProcessError, so if the command fails for any reason, it will raise an exception. This will cause the upgrade thread to be interrupted, but the updater will continue to run. The result from the user's point of view is a frozen updater. We should catch this error, and properly abort the update and report it.

[zenmonkeykstop]

Still an issue, moving to securedrop-updater repo