conf_file.qemu_conf: Add test for auto_dump_*

Test auto_dump_* parameter in qemu.conf.

1) Change auto_dump_* in qemu.conf;
2) Restart libvirt daemon;
4) Check if file open state changed accordingly.

Signed-off-by: Hao Liu <hliu@redhat.com>
Merge pull request #324 from Hao-Liu/auto_dump

conf_file.qemu_conf: Add test for auto_dump_*