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

This reverts commit e419d922.

After much discussion the commit being reverted has and would have
generated more work than problems solved.

Before this commit, Daniele had hardcoded into the CTA
front-end the constraint that CTA admins must be
authenticated by krb5.

This commit drops this contraint for two reasons:

1. The xrootd/EOS configuration files already require
   operators to specify which authentication methods can
   be used.  Daniele’s constraint is not needed to
   further enforce security, it only serves to constrain
   admin authentication to krb5 which I personally do not
   see as providing any added value.

2. The CERN infrastructure uses krb5, other sites like
   RAL do not.

Added drive status reporting in scheduler
Added drive status reporting in OStoreDB
Added support for drive status listing in the front end
Removed virtual functions from the Scheduler, which is never overloaded.
Added DesiredDriveState structure to drive state.
Removed usage of duplicate MountType, DriveStatus and DriveState structures.
Created DriveInfo structure to allow recreation of drive register entry in all
reporting situation (potentially with partial/assumed info).

Removed the reconciliation command (will be done by EOS: both the CTA side and the EOS side reconciliation)

Added stub for supporting disk instance authorization (to be discussed how to implement this in the catalogue)