Remove most `System.exit()` calls in various security tools and only leave one in the `main` method. This paves the way to convert them to JSR 199 tools.
------------- Commit messages: - the fix Changes: https://git.openjdk.org/jdk/pull/15951/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15951&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8316964 Stats: 480 lines in 8 files changed: 286 ins; 107 del; 87 mod Patch: https://git.openjdk.org/jdk/pull/15951.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/15951/head:pull/15951 PR: https://git.openjdk.org/jdk/pull/15951
