virttest.libvirt_vm: Add functions to get device details.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test: Add functions for remote disk operations.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test: Support lvm for RemoteDiskManager.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test.libvirt: Add attaching operations for libvirt vm.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
utils_test.init: Add function for RemoteDiskManager.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
Merge pull request #1610 from yumingfei/disk_operations

Add some functions for disk operations