sstable: move_to_new_dir: rm TOC last
sstable: move_to_new_dir: rm TOC last

To facilitate cleanup on crash, first rename the TOC file to TOC.tmp,
and keep until all other files are removed, finally remove TOC.tmp.

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

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