Some subcommands of 'swift-manage-shard-ranges' prompt a user before
taking action. For example, 'find_and_replace --enable' will warn a
user and ask for input if existing shard ranges are found. This patch
improves user input handling to exit gracefully (with err code 3) if
either an EOFError or KeyboardInterrupt is raised while waiting for
user input.
Co-Authored-By: Tim Burke <tim.burke@gmail.com>
Change-Id: I75c8acd372d449b8a4531ff816d839dfe40d8a56