Don't exit if the libvirtd config does not exist

It is common for the $HOME/.libvirt/libvirtd.conf file to not
exist. Treat this situation as non-fatal since we can carry
on with our default settings just fine.

* daemon/libvirtd.c: Treat ENOENT as non-fatal when loading
  config

daemon/libvirtd.c

@@ -1028,6 +1028,10 @@ daemonConfigLoad(struct daemonConfig *data,
 {
     virConfPtr conf;
 
+    if (access(filename, R_OK) == -1 &&
+        errno == ENOENT)
+        return 0;
+
     conf = virConfReadFile (filename, 0);
     if (!conf)
         return -1;