tests/qtest/migration: Move a couple of slow tests under g_test_slow

The xbzrel and vcpu_dirty_limit are the two slowest tests from
migration-test. Move them under g_test_slow() to save about 40s per
run.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240911145204.17692-1-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
1 file changed