WAL logs in archive mode will consume a lot more spaces and not useful
when backup is off. This fix add ability to switch WAL logs mode based
on the backup switch.
You may see this error if you use pgsql 9.5 with 9.4 data.
> FATAL: database files are incompatible with server
> DETAIL: The data directory was initialized by PostgreSQL version 9.4, which is not compatible with this version 9.5.0.