High: config: allow configuring more than one ticket (bnc#889806)

For whatever reason I assumed at the time that there'd be only
one ticket (b3f65f0). The ticket validation was also skipped for
the last ticket (7386381). This commit fixes both issues.
Medium: config: prevent segfaults on bad usage
Low: ticket: print INF instead of N/A on unknown expiry time (reverts 7830e3f)
Dev: test: relax timing in split_leader
Medium: ticket: drop expired tickets in elections too (gh#17)
Dev: test: fix invoking netem without args
Dev: test: don't reset netem more than once
Dev: test: fix logging for __netem__
Dev: test: set ssh StrictHostKeyChecking=no
Dev: test: log locally when setting netem
Dev: test: support multiple netem qdisc