CB-4531 bin/check_reqs scripts exit with code 2 on error

- Return ERROR_VALUE/NOTIMPLEMENTED_VALUE
- Restore number path for symmetry with install-emulator, install-device, build
- Refactor exit_handler into utils

Reviewed by James Keshavarzi <jkeshavarzi@blackberry.com>
Tested by Jenny Gee <jgee@blackberry.com>