restore and pg_control

[gsmolk]

To prevent instance from starting in the middle of restore:

1. When running regular restore, we must copy pg_control at the very end.
2. When running incremental restore, we must drop pg_control first.

[gsmolk]

INFO: Running incremental restore into nonempty directory: "/data/postgresql"
INFO: Trying to read pg_control file in destination direstory
ERROR: Could not open file "/data/postgresql/global/pg_control" for reading: No such file or directory