ntp: check name and return status from NSR_AddSourceByName()

Return an error status when the name is not printable or contains a
space (don't bother with full hostname validation). If the name is an
address, return the same status as NSR_AddSource(). Otherwise, return a
"not resolved yet" status.

cmdmon.c

@@ -729,6 +729,8 @@ handle_add_source(NTP_Source_Type type, CMD_Request *rx_message, CMD_Reply *tx_m
       tx_message->status = htons(STT_INVALIDAF);
       break;
     case NSR_NoSuchSource:
+    case NSR_InvalidName:
+    case NSR_UnresolvedName:
       assert(0);
       break;
   }
@@ -755,6 +757,8 @@ handle_del_source(CMD_Request *rx_message, CMD_Reply *tx_message)
     case NSR_TooManySources:
     case NSR_AlreadyInUse:
     case NSR_InvalidAF:
+    case NSR_InvalidName:
+    case NSR_UnresolvedName:
       assert(0);
       break;
   }