When using the sync option, the migration status is not set away from idle during sync operations

Problem/Motivation

When using the --sync option, which is processesed with the PRE_IMPORT event, the migration status, is idle during the sync operation. This is because MigrateExecutable::import() is changing the status after it fires the event. If you are relying on the status somewhere else in your application, this can cause problems.

Steps to reproduce

Start a migration with the sync flag and y long lasting sync operation and check the migration status via UI, drush or in code.

Proposed resolution

Set the migration status in MigrationImportSync::sync() during sync operations.