mgr/diskprediction_local: Reverted dependencies, added HGST models

mgr/diskprediction_local: Reverted dependencies, added HGST models

Removed pandas from requirements.txt, ceph.spec.in, and debian/control
because of installation issues in RHEL/CentOS.

Replaced pandas usages in RHDiskFailurePredictor with similar numpy
counterparts (e.g. structured array instead of dataframe)
Replaced joblib usages with pickle because older version of scikit-learn
did not list joblib as a dependency and so it wasnt getting installed.
Using joblib would have required specifying it as a separate dependency
in spec file and requirements.

Added HGST models for RHDiskFailurePredictor.

Signed-off-by: Karanraj Chauhan <kachauha@redhat.com>