nwfilter: Remove Coverity DEADCODE warning

The nwfilterStateInitialize() would only assign sysbus inside
a WITH_DBUS conditional, thus leaving a subsequent check for sysbus
and nwfilterDriverInstallDBusMatches() as a no-op

Rather than try to add WITH_DBUS conditions which ended up conflicting
with the usage of HAVE_FIREWALLD conditionals, just remove the WITH_DBUS
since virdbus.c has entry points for with and without conditions.

src/nwfilter/nwfilter_driver.c

@@ -177,11 +177,9 @@ nwfilterStateInitialize(bool privileged,
     if (!privileged)
         return 0;
 
-#if WITH_DBUS
     if (virDBusHasSystemBus() &&
         !(sysbus = virDBusGetSystemBus()))
         return -1;
-#endif /* WITH_DBUS */
 
     if (VIR_ALLOC(driverState) < 0)
         return -1;