Add error as not-in-progress migration status

When a migration status becomes "error" the migration is no longer
in progress, i.e. it is in a terminal state.  However, the
migration_get_in_progress_by_host_and_node method returns migrations
that have an "error" status, causing, among other things, the
Resource Tracker to continually log messages about how an
Instance is not resizing, creating excessive noise in the logs,
especially since the fact that a migration is entering the "error"
status is already logged.  This change causes "error"-status
migrations to not be included when retrieving "in progress"
migrations.

Closes-Bug: #1258275

Change-Id: I67bfec9f91f89ff38422469a5d86e14c4fffa40b
Merge "Add error as not-in-progress migration status"