compaction: log info message when interrupting compaction
compaction: log info message when interrupting compaction

Info messages are logged when compaction jobs start and finish
but there is no message logged when the job is interrupted, e.g.
when stopped by the compaction_manager.

Refs scylladb/scylla-dtest#2468

Signed-off-by: Benny Halevy <23c997c90eb8537635e9392d48e7af1bf1b2ca22@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla