Add a timeout argument to run_rsync
Add a timeout argument to run_rsync

If a timeout is specified (not the default), we spawn a new thread that
will check on the process after ``timeout`` seconds and if the process
is still running, it will kill it.

fixes https://github.com/fedora-infra/mirrormanager2/issues/77

pombredanne/mirrormanager2,pombredanne/mirrormanager2,pombredanne/mirrormanager2,pombredanne/mirrormanager2