Improve error handling in p0f plugin

[flimzy]

• This corrects a specific bug, where a socket connection failure was never reported (due to reporting $@ instead of $!)
• And it makes all the present error logs more meaningful by mentioning 'p0f'

[msimerson]

And it makes all the present error logs more meaningful by mentioning 'p0f'

Does this not just make all them error messages more redundant? Last I checked, plugin log messages look like this:

@4000000054a2ff8d077dfddc 98226 (connect) ident::p0f: FreeBSD 9.x or newer

So before you change, an example error message was:

@4000000054a2ff8d077dfddc 98226 (connect) ident::p0f: skip, unable to determine remote IP

and now it's:

@4000000054a2ff8d077dfddc 98226 (connect) ident::p0f: skip p0f, unable to determine remote IP

[jaredj]

@msimerson what is responsible for prepending '(connect) ident::p0f: '? perhaps it's something that doesn't exist in our fork yet... or doesn't exist in upstream yet? :)

[msimerson]

@jaredj, I dunno. QP has done that for as long as I've used it.

[msimerson]

what is responsible for prepending (connect) ident::p0f:?

lib/Qpsmtpd::varlog

[flimzy]

I suspect the code to prepend the plugin name, etc, is missing or non-functional in our fork, then. I'm in favor of rolling back that particular commit here, and investigating further on our fork.

[jaredj]

Not exactly; see issue #182

At any rate this PR has already been un-merged