qemu: command: Extract blkdeviotune checks into a separate function
qemu: command: Extract blkdeviotune checks into a separate function

qemuBuildDriveStr grew into 'megamoth' proportions. Cut out some parts.

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