Regression test portability: run-test.sh

- Check for pidof(8) presence. It may not be present on non Linux systems
- Add a -f flag to run-tests.sh to bypass utility presence checks

Submit again because of spurious regression test failure

BUG: 764655
Change-Id: Iee6282c686c63a01808543054f8e5a3b5b79fca2
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/8279
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Harshavardhana <harsha@harshavardhana.net>
Tested-by: Harshavardhana <harsha@harshavardhana.net>