Fix 'tee' command in mysql client. (Bug #8499)

client/mysql.cc:
  A va_list can't be reused without being copied or reset, so
  don't try to reuse it in tee_fprintf().

client/mysql.cc

@@ -3073,9 +3073,14 @@ void tee_fprintf(FILE *file, const char *fmt, ...)
 #ifdef OS2
   fflush( file);
 #endif
+  va_end(args);
+
   if (opt_outfile)
+  {
+    va_start(args, fmt);
     (void) vfprintf(OUTFILE, fmt, args);
-  va_end(args);
+    va_end(args);
+  }
 }