journald: minor fixes

journald: minor fixes

This primarily contains some minor coding style fixups for 7a24f3bf2fb181243a1957a0cdd54cd919396793 and earlier changes. Specifically:

* Don't log at log levels above LOG_DEBUG from "library" code like journal-file.c

* Don't negate errno values before passing them to log_debug_errno(), as the call can handle this fine anyway

* Cast some calls we knowingly ignore the return values of to (void)

* Don't clobber function call-by-ref return values on failure

* Don't mix function calls and variable declarations in one line

There's also one more relevant change: when failing to enqueue a journal change fs event, we'll run it immediately.