In RAND_write_file, truncate the file to the no. of bytes written

(we're now using fopen(..., "rb+") instead of fopen(..., "wb"),
so the file is not truncated automatically).

crypto/rand/randfile.c

@@ -167,6 +167,8 @@ int RAND_write_file(const char *file)
 		ret+=i;
 		if (n <= 0) break;
 		}
+	if (ret > 0)
+		ftruncate(fileno(out), ret);
 	fclose(out);
 	memset(buf,0,BUFSIZE);
 err: