Workers are resilient and will retry to establish a sync flow when something
happens. This resulted in incomplete files. A worker now keeps the filesystem
clean, cleaning up old files only once a dump is established.

The above was for internal cleanup only. A config flag, cleanup, has been
added to control whether old files should be removed when a new worker
establishes itself. Setting this to true should result in a single .rdb and
.aof file. Setting it to false should result in an .rdb and .aof file at each
TTL.