udevd: daemon - connect /dev/null to std{in,out,err} in debug mode

This is essentially a revert of 5c67cf2 and fixes issue #190.

src/udev/udevd.c

@@ -43,6 +43,7 @@
 #include "sd-daemon.h"
 #include "sd-event.h"
 
+#include "terminal-util.h"
 #include "signal-util.h"
 #include "event-util.h"
 #include "netlink-util.h"
@@ -1687,6 +1688,10 @@ int main(int argc, char *argv[]) {
 
                 log_info("starting version " VERSION);
 
+                /* connect /dev/null to stdin, stdout, stderr */
+                if (log_get_max_level() < LOG_DEBUG)
+                        (void) make_null_stdio();
+
                 pid = fork();
                 switch (pid) {
                 case 0: