tests/qtest/migration: Add tests for file migration with direct-io

The tests are only allowed to run in systems that know about the
O_DIRECT flag and in filesystems which support it.

Note: this also brings back migrate_set_parameter_bool() which went
away when we removed the compression tests. I copied it verbatim.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
3 files changed