hmp: migrate command (without -d) now blocks correctly

This patch fixes a timing issue that migrate command (without -d) does not
block in some cases.

The original version of hmp.c:hmp_migrate_status_cb checks if the
migration status is 'active' or not to detect the completion of a migration.

However, if this function is executed when the migration status is stil
'setup' (the status before 'active'), migration command returns
immediately even if the user does not specify -d option.

Signed-off-by: Soramichi Akiyama <akiyama@nii.ac.jp>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
