Previously, Litestream would avoid closing the SQLite3 connection
in order to ensure that the WAL file was not cleaned up by the
database if it was the last connection. This commit changes the
behavior by introducing a file control call to perform the same
action. This allows us to close the database file normally in all
cases.
This commit changes the `replicate` command so that it performs a
final DB sync & replica sync before it exits to ensure it has
backed up all WAL frames at the time of exit.
This commit reverts 4e469f8 which was used for debugging the validation
stall corruption issue. It can cause the disk to fill with temporary
files though so it is being reverted.
