Spool migration phases

The following JES2 spool migration phases all pertain to the source spool volume. SYSLOG status messages indicate whether the migration is a move migration or a merge migration.

PENDING: Awaiting start of migration.
INITIALIZING: General migration configuration work is being done, such as creating subtasks, data structures, and XCF mailboxes.
SETUP: Setup for a migration is being done. All MAS members participate in this process.
COPY: The dataset on the source spool volume has been migrated to the target spool volume. Runtime changes are coordinated and tracked by the migrator.
CATCHUP: Tracks that were changed by runtime operations during the COPY phase are being recopied.
CANCEL: Migrator subtask cleanup is being done because an operator cancelled the active migration or the migration process encountered an error.
BACKOUT: Updates are being backed out because an operator cancelled the active migration or the migration process encountered an error.
CLEANUP: General cleanup is being done at the end of the migration.