imsm: More precise message when spanned raid is created
When RAID is created between VMD and SATA disks, printed message is
"Mixing devices attached to different VMD domains is not allowed". This message
is unclear and misleading because creating spanned containers between different
VMD domains is allowed. Set error message to more precise text.
Signed-off-by: Michal Zylowski <michal.zylowski@intel.com> Signed-off-by: Jes Sorensen <jsorensen@fb.com>