Regression test portability: stat

Linux uses stat -c, stat --printf= or stat --printf
NetBSD uses stat -f with different format strings. This change set
changes all stat usage to stat -c and introduce a shell stat()
fonction to perform the format string translation.

BUG: 764655
Change-Id: I024fca7c1b736b053f5888cbf21da0a72489ef63
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/8424
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Harshavardhana <harsha@harshavardhana.net>
Tested-by: Harshavardhana <harsha@harshavardhana.net>