cgpt: unify cli int parsing error checking

Most of the cmd funcs had the same logic copied & pasted multiple times
over.  Unify them into a common header.

BUG=chromium:644845
TEST=precq passes
TEST=passing invalid args to some funcs is caught
BRANCH=None

Change-Id: Ib7212bcbb17da1135b2508a52910aac37ee8e6cd
Reviewed-on: https://chromium-review.googlesource.com/382691
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
10 files changed