mdns: Set error when failing due to missing avahi

When building without avahi support, we used VIR_DEBUG() to note that to
the user.  However, functions that fail because of that (return NULL/-1)
did not set the error message.  This was the only file that forgot to do
such thing.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

src/rpc/virnetservermdns.c

@@ -617,14 +617,14 @@ static const char *unsupported = N_("avahi not available at build time");
 virNetServerMDNS *
 virNetServerMDNSNew(void)
 {
-    VIR_DEBUG("%s", _(unsupported));
+    virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _(unsupported));
     return NULL;
 }
 
 int
 virNetServerMDNSStart(virNetServerMDNS *mdns ATTRIBUTE_UNUSED)
 {
-    VIR_DEBUG("%s", _(unsupported));
+    virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _(unsupported));
     return -1;
 }
 
@@ -632,7 +632,7 @@ virNetServerMDNSGroupPtr
 virNetServerMDNSAddGroup(virNetServerMDNS *mdns ATTRIBUTE_UNUSED,
                          const char *name ATTRIBUTE_UNUSED)
 {
-    VIR_DEBUG("%s", _(unsupported));
+    virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _(unsupported));
     return NULL;
 }
 
@@ -648,7 +648,7 @@ virNetServerMDNSAddEntry(virNetServerMDNSGroupPtr group ATTRIBUTE_UNUSED,
                          const char *type ATTRIBUTE_UNUSED,
                          int port ATTRIBUTE_UNUSED)
 {
-    VIR_DEBUG("%s", _(unsupported));
+    virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _(unsupported));
     return NULL;
 }