Fix #3210 about slow restore with bvfs
Fix #3210 about slow restore with bvfs

The BSR creation procedure is expecting to have ordered FileIndex,
this is now done with an extra SORT.

rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula