Remove cruft
Update mock/stubs to avoid deprecations
Force subprocess to exit after timeout

Fixes MIXLIB-16.

This issue is particularly prominent when yum/rpm commands go off the
deep end repeatedly, but affects any case where a process takes longer
than the timeout to complete.
Cleanup control flow in main loop

removes some complexity that was introduced with the fix to kill
timed-out child processes
Add logging about timed-out cmd termination when possible

If a logger is configured, send `error` level messages about child
process termination for timeout violations.
Add termination info to error messages

If no logger is configured, we still want to inform the user that the
process was killed (and how).
Merge branch 'MIXLIB-16'