Server test: Adds support for multi-host migration in afe tool.

Test name Multi_host migration.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
server: Multi-host migration control file repair.

This patch makes multi-host test working with changes virt test.
subtest.cfg is automaticali generated by script.

Signed-off-by: Jiří Župka <jzupka@redhat.com>