Some scripts contained `false` for returning 1 to callers instead of
`exit 1` and that works like:
$ false
$ echo $?
1
$
But that made confusion in a PR review process.
So this replaces `false` with `exit 1` for long-term maintenance.
The ./third_party/* directory contains scripts, libraries and
other components from external sources. These should be omitted
from lints and checks with the exception of things that are
forked and modified (located in ./third_party/forked/*) for
project related reasons.
Both verify-golint.sh and verify-shellcheck.sh have the same logic
which checks failure_file in alphabetical order.
In addition, we'd like to add another script which requires the
same logic. So this add a common function for cleanup.