The scheduling based on disk throughput estimates will not be implemented in the forseeable, if ever.

Ported CASTOR-5433: Tapeserverd accessing xroot files might not close properly due to uninitialized variable

Moved XrootCl exception and thrower to cta::exception

Before this commit, column metadata was only set on the first call
to SqliteRset::next().  This was a design bug.  Column metadata can
be different for different rows in a result set.  This is because a
NULL column value has a corresponding SQLITE_NULL datatype.

The cleaner is started if a tape could be in the drive after a session crashed. This depends on the previous
sesion state.
If a cleaner crashes, the next session will put the drive down.
The sessions do not fully report their states yet.

The Shutdown state can only be used internally by the DriveHandler after process exit.

Added one second sleeps when uncaught exceptions show up to avoid fast looping in the presence of bugs.

Added exception lauching for sqlite call that returned NULL in some cases (DB might have been corrupted).