migration: Convert do_info_migrate() to QObject

migration: Convert do_info_migrate() to QObject

Return a QDict, which may contain up to more two QDicts, depending
on the type of migration we're performing.

IMPORTANT: as a QInt stores a int64_t integer, RAM values are going
to be stored as int64_t and not as uint64_t as they are today. If
this is a problem QInt will have to be changed.

This commit should not change user output.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit c86a668390d16d6b3249acd50bfa61ad825c7a80)