CONC-667: Fix statement handling when unbuffered results are pending.

Resetting a statement will result in an error, if another (different)
statement has a pending unbuffered result set (CR_COMMANDS_OUT_OF_SYNC).

Freeing a statement result set will return an error, if the statement
has no result set or was not executed (CR_STMT_NO_RESULT).

libmariadb/ma_errmsg.c

@@ -118,6 +118,7 @@ const char *mariadb_client_errors[] =
   /* 5021 */ "Binary log error (File: %.*s start_pos=%ld): %s.",
   /* 5022 */ "File '%s' is not a binary log file",
   /* 5023 */ "Semi sync request error: %s",
+  /* 5024 */ "Statement has no result set",
   ""
 };