Not all errors are detected

[eigood]

When dig is not installed, the ip=$(dig) line is non-sensible. Later, when ssh-keygen and ssh-keyscan are called, they end up returning bad values, and the script result back to ansible ends up saying changed=false, but otherwise there is no error.

To fix this, use 'set -e', 'trap _onexit EXIT', and properly return a real error.

If exiting the script successfully, then remove the trap by "trap '' EXIT".

These commands are POSIX, so are safe to use.

ps: this script to actually be /bin/sh, if one used && instead of -a when doing [, and used = instead of ==,

pps: I could also make a fork/pull request for this too, if the above is not clear