Add tests for managedsave command.

Test bypass_cache option
Test bypass_cache and start_delay option in libvirt-guests configuration file.
There are 3 vms are used in this test. Although it take some more time, I think it's more efficient to use clone than preparing vms before the test. If we provide many VMs in environment, every test will start/stop/check status these unused Vms. It will waste more time. right?