Fix printing of Server Re-Failed and Server Faults.

nfsstat -s prints bogus large numbers for the Server Re-Failed and Server
Faults fields. This was introduced by r328588.
Although I know nothing about libxo, these lines aren't titles and this
patch seems to fix the problem, so I am committing it for rea@ who emailed
it to me.
It also deleted the trailing ':' from the title lines, since those were not
in the pre-r328588 output.

If there is a more correct fix, someone conversant with libxo will need
to do so.

Submitted by: rea
MFC after: 2 weeks