core: don't reset log level to NOTICE if we get quiet on the kernel cmdline

core: don't reset log level to NOTICE if we get quiet on the kernel cmdline

quiet should really just have an effect on the stuff we dump on the
console, not what we log elsewhere.

Hence:

        debug on kernel cmdline → interpreted by every tool, turns up
        log levels to "debug" everywhere.

        quiet on kernel cmdline → interpreted only by PID 1 (and
        obviously the kernel) no alteration of the max log level, but
        turns off status output.

http://lists.freedesktop.org/archives/systemd-devel/2014-December/026271.html