util: Add virCgroupGetBlockDevString
util: Add virCgroupGetBlockDevString

This function translates device paths to "major:minor " string, and all
virCgroupSetBlkioDevice* functions are modified to use it.  It's a
cleanup with no functional change.

Signed-off-by: Martin Kletzander <e82f23e74d43760279ebcc505dac4ae70d5627d0@redhat.com>

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