Fixes #5221: Cleanup ncf post hooks and make the output of the commands ...

...silent unless an error happens to prevent log cluttering

Ticket: http://www.rudder-project.org/redmine/issues/5221

To be merged in 2.11

NOTE: This is only cleanup/comment code, no logic has been altered.
Because it is just like using cat | grep :)

From grep's man page:
```
       -c, --count
              Suppress normal output; instead print a count of matching lines for each input file.  With the -v, --invert-match  option  (see  below),  count  non-
              matching lines.  (-c is specified by POSIX.)
```

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