udevd: respect the log-level set in /etc/udev/udev.conf

A regression introduced when we moved to systemd's logging is that the only
way to adjust the log-level of the udev daemon is via the env var, kernel
commandline or the commandline.

This reintroduces support for specifying this in the configuration file.

src/udev/udevd.c

@@ -923,7 +923,10 @@ int main(int argc, char *argv[])
         log_set_target(LOG_TARGET_AUTO);
         log_parse_environment();
         log_open();
+
         udev_set_log_fn(udev, udev_main_log);
+        log_set_max_level(udev_get_log_priority(udev));
+
         log_debug("version %s\n", VERSION);
         label_init("/dev");