translate_open_mode_posix_to_stream: guard against invalid/unsupported oflags

[SwooshyCueb]

As noted in #2148 (comment) , translate_open_mode_posix_to_stream in s3_operations.cpp does not guard against invalid/unsupported values passed in via oflag:

irods_resource_plugin_s3/s3/s3_operations.cpp

Lines 423 to 455 in d4904e4

	std::ios_base::openmode translate_open_mode_posix_to_stream(int oflag, const std::string& call_from) noexcept
	{
	using std::ios_base;
	std::uint64_t thread_id = std::hash<std::thread::id>{}(std::this_thread::get_id());
	logger::debug("{}:{} ({}) [[{}]] call_from={} O_WRONLY={}, O_RDWR={}, O_RDONLY={}, O_TRUNC={}, O_CREAT={}, O_APPEND={}",
	__FILE__, __LINE__, __FUNCTION__, thread_id, call_from.c_str(),
	(oflag & O_ACCMODE) == O_WRONLY, (oflag & O_ACCMODE) == O_RDWR, (oflag & O_ACCMODE) == O_RDONLY,
	(oflag & O_TRUNC) != 0, (oflag & O_CREAT) != 0, (oflag & O_APPEND) != 0);
	ios_base::openmode mode = 0;
	if ((oflag & O_ACCMODE) == O_WRONLY || (oflag & O_ACCMODE) == O_RDWR) {
	mode |= ios_base::out;
	}
	if ((oflag & O_ACCMODE) == O_RDONLY || (oflag & O_ACCMODE) == O_RDWR) {
	mode |= ios_base::in;
	}
	if ((oflag & O_TRUNC) || (oflag & O_CREAT)) {
	mode |= ios_base::trunc;
	}
	if (oflag & O_APPEND) {
	mode |= ios_base::app;
	mode &= ~ios_base::trunc; // turn off trunc flag
	}
	return mode;
	}

[korydraughn]

This is specifically about making sure the value of O_ACCMODE is valid.