dispatcher: set G_LOG_DOMAIN to "nm-dispatcher"

Originally, we would define G_LOG_DOMAIN via CFLAGS arguments.
Since commit 341b6e0704 ('all: change G_LOG_DOMAIN to "nm"') we would
instead set it in source and uniformly define it as "nm".

The reasons are that most parts of our source should not use g_log() directly,
and there is an aim to avoid special CFLAGS to simplify the build setup.

However, dispatcher indeed uses g_log() for logging, so the value there
is important.

Fix that, but this time by setting the define in source not via
CFLAGS.

Fixes: 341b6e0704 ('all: change G_LOG_DOMAIN to "nm"')

src/libnm-std-aux/nm-default-std.h

@@ -12,7 +12,9 @@
     #error Dont define NETWORKMANAGER_COMPILATION
 #endif
 
-#define G_LOG_DOMAIN "nm"
+#ifndef G_LOG_DOMAIN
+    #define G_LOG_DOMAIN "nm"
+#endif
 
 /*****************************************************************************/
 

src/nm-dispatcher/nm-dispatcher.c

@@ -3,6 +3,8 @@
  * Copyright (C) 2008 - 2012 Red Hat, Inc.
  */
 
+#define G_LOG_DOMAIN "nm-dispatcher"
+
 #include "libnm-client-aux-extern/nm-default-client.h"
 
 #include <syslog.h>