qemu: hot-plug: Fix broken SCSI disk hot-plug
qemu: hot-plug: Fix broken SCSI disk hot-plug

The commit "qemu: hot-plug: Assume support for -device in
qemuDomainAttachSCSIDisk" dropped the code for the automatic SCSI
controller creation used in SCSI disk hot-plugging. If we are
hot-plugging a SCSI disk to a domain and there is no proper SCSI
controller defined, it results in an "error: internal error: Could not
find scsi controller with index X required for device" error.

For that reason reverting a hunk of the commit
d4d32005d6e8b2cc0a2f26b483ca1de10171db6d.

This patch also adds an extra comment to the code to clarify the
loop.

Reviewed-by: Boris Fiuczynski <2648abdd55bfebf313fd324b464b047e6eea300e@linux.vnet.ibm.com>
Reviewed-by: Bjoern Walk <40545c009452f40d2ae0bbfbd987b332d274d328@linux.vnet.ibm.com>
Signed-off-by: Marc Hartmayer <7bafc8cd4e6394916d396e4f8cde69753be8d066@linux.vnet.ibm.com>

fabianfreyer/libvirt,VenkatDatta/libvirt,taget/libvirt,nertpinx/libvirt,olafhering/libvirt,datto/libvirt,VenkatDatta/libvirt,taget/libvirt,jfehlig/libvirt,andreabolognani/libvirt,crobinso/libvirt,datto/libvirt,crobinso/libvirt,jardasgit/libvirt,jardasgit/libvirt,olafhering/libvirt,andreabolognani/libvirt,nertpinx/libvirt,zippy2/libvirt,libvirt/libvirt,libvirt/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,nertpinx/libvirt,jardasgit/libvirt,jardasgit/libvirt,nertpinx/libvirt,eskultety/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,taget/libvirt,olafhering/libvirt,jfehlig/libvirt,taget/libvirt,libvirt/libvirt,jardasgit/libvirt,andreabolognani/libvirt,zippy2/libvirt,eskultety/libvirt,olafhering/libvirt,zippy2/libvirt,taget/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,datto/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,libvirt/libvirt,datto/libvirt,eskultety/libvirt,eskultety/libvirt,zippy2/libvirt,eskultety/libvirt,crobinso/libvirt,datto/libvirt,nertpinx/libvirt,andreabolognani/libvirt,crobinso/libvirt,andreabolognani/libvirt