staging: lustre: obd_mount: use correct niduuid suffix.

Commit 4f016420 ("Staging: lustre: obdclass: Use kasprintf") moved
some sprintf() calls earlier in the code to combine them with
memory allocation and create kasprintf() calls.

In one case, this code movement moved the sprintf to a location where the
values being formatter were different.
In particular
       sprintf(niduuid, "%s_%x", mgcname, i);
was move from *after* the line
        i = 0;
to a location where the value of 'i' was at least 1.

This cause the wrong name to be formatted, and triggers

       CERROR("del MDC UUID %s failed: rc = %d\n",
              niduuid, rc);

at unmount time.

So use '0' instead of 'i'.

Fixes: 4f016420 ("Staging: lustre: obdclass: Use kasprintf")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>