Share task_state was set to migration_success
before completing migration. There was still
updates to the share model to be performed
before completing.
Also, small refactoring in host-assisted
migration's migration_complete that was not
setting the task_state migration_completing
at the proper time, allowing a bigger window
for 2 concurrent migration_complete calls.
Change-Id: I88df15446ffe34f3f12770d53c3e03d232f495c2
Closes-bug: #1665072
