MXS-1996: Remove misleading errors

The errors are expected if the file is empty.

avro/maxavro_file.c

@@ -317,7 +317,6 @@ MAXAVRO_FILE* maxavro_file_open(const char* filename)
             }
             else
             {
-                MXS_ERROR("Failed to initialize avrofile.");
                 maxavro_schema_free(avrofile->schema);
                 error = true;
             }

server/modules/routing/avrorouter/avro_index.c

@@ -172,10 +172,6 @@ void avro_index_file(AVRO_INSTANCE *router, const char* filename)
 
         maxavro_file_close(file);
     }
-    else
-    {
-        MXS_ERROR("Failed to open file '%s' when generating file index.", filename);
-    }
 }
 
 /**