Re-enables the SC reload capabilities for OverlayManager on service start. Fixes EUCA-5040.

During SC startup in OverlayManager it will scan the DB and attempt to re-export any volumes
that were exported (had iscsi targets) on last shutdown. The decision is made based on the
presence of a loopback device name in the DB. The reload process will restore loopbacks,
assign new ones if the previous is taken by another resource, and ensure that LVM LVs are
enabled and iSCSI targets reconstructed. If volume is already exported (i.e. just a service
restart instead of a machine reboot), then the process cleanly leaves existing resources
untouched.

Also adds many INFO level log messages to track process during startup. Grep for 'SC Reload'
in the cloud-output.log to see the process.