core: New Error Message for an IDE Hot Plug

Hot plugging a disk to an IDE interface is currently not supported at
all (by any OS). Thus, the previous error message saying that the guest
OS version is not supported is irrelevant.

Change-Id: I10acfe04f2089708de7212b179d5e3d71edb4a12
Bug-Url: https://bugzilla.redhat.com/1126547
Signed-off-by: Idan Shaby <ishaby@redhat.com>