history: Remove of datacenter storage_type

This patch removes the storage type of a datacenter, instead a
datacenter can be marked as is_local_storage - contains local on
host storage or shared - contains shared storages of various types.

Change-Id: I948a8b15fdfb5c8fd9dd9f272a371a48657c0113
Related-To: https://bugzilla.redhat.com/1038053
Signed-off-by: Shirly Radco <sradco@redhat.com>