tools/pre-commit: Complete all checks on all files before exiting with Ok/Fail status.

Change-Id: Iea6df6fbe5a977b282e823f87cd9f760e92a3e22
Reviewed-on: https://code.wireshark.org/review/2918
Reviewed-by: Bill Meier <wmeier@newsguy.com>
(cherry picked from commit cdf6d62b3ba81fd40ab386f5b0b16ec61223f5a9)
Reviewed-on: https://code.wireshark.org/review/2947