This was seen while debugging/working on LU-16786

In case (corner) where type=disk and targets/ostnames are repeated the obdfilter-survey throws "error: attach: File exists". This is because the on first iteration the attach and setup is already done. It is not a fatel error the run still continues but for second ost it fails to attach.

Reproducer:

$ NETTYPE=tcp thrlo=2 nobjhi=1 thrhi=4 size=231 case=disk rslt_loc=/tmp targets="lustre-OST0000 lustre-OST0000" ./lustre-iokit/obdfilter-survey/obdfilter-survey
<snip>
"error: attach: File exists"
<snip>