Currently, --shared-migration and --block-migration options effects are
reversed: --block-migration requests a migration with share,
--shared-migration a block-migration.
This change corrects OSC implementation and clarifies arguments passed
to novaclient (the root cause of the bug).
Change-Id: Ib682cff0c44d3b1304670f8606907b1762d8b1e7
Closes-Bug: #1518059