grep: fix combination of quiet and count flag

When the quiet (-q) flag is provided, we don't expect any output.
Currently, the behavior is broken:
$ grep -cq flag util.c
1

$ grep -cs flag util.c
55

First of all, we print a number to stdout. Secondly, it just returns
0 or 1 (which is unexpected). GNU grep with c and q flags doesn't
print anything.

Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D31108

(cherry picked from commit 24c681a7f6d6c777221fdbd289da64ff65ad8785)