Duplicate mount entry shown in df, possibly when mounting NFS share

Issue

• Output of the df command after mounting NFS share:

    Filesystem           1K-blocks      Used Available Use% Mounted on 
    /dev/sdb1              2087840    607944   1374672  31% / 
    /dev/sdb5              5076284   3953572    866880  83% /var 
    /dev/sdb6              5076284   3248432   1572020  68% /usr 
    ...
    /dev/sdb9              4167768   2512068   1445652  64% /opt 
    example.com:/net  45721856  35799424   7599840  83% /net 
    example.com:/net  45721856  35799424   7599840  83% /net