Revert "Periodically call sd_journal_process in journalctl" (#8147)

This reverts commit 992149c0.

https://github.com/systemd/systemd/pull/8144#issuecomment-364464627
$ (set -o pipefail; sudo ./build/journalctl --no-pager | wc -l; echo $?)
Failed to process inotify events: Bad file descriptor
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