libvirt.tests: Unify paramters for migration tests.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
tests.migrate: Remove copy_storage testcases from live migration.

Migrate vm with --copy-storage-all/--copy-storage-inc work not
well with live migration.And since it's already complemented
in virsh.migrate_copy_storage, remove them here.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
tests.migrate: Create a vm automatically for --dname.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
tests.migrate: Fix problems for compcache.

 * Parameter remote uri should be compcache_remote_uri.
 * The showup time of domjob for compcache may be narrow.
   So get job_type and compression cache at same time to avoid miss.
 * Fix a typo.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
Pass load_vms instances for stress.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
Scsi device supports only qcow2 format.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
Merge pull request #358 from yumingfei/unit_migration

Unit migration parameters and some enhancements