Return correct status if touch failed

[artonge]

When uploading a file to an external s3 bucket, the original mtime is not kept. It boils down to the touch operation being deactivated for existing file for s3 buckets. Limitation introduced here: #21734

This PR changes the return value of the touch method. Now this method returns false when the file already exists to trigger the following condition:

server/lib/private/Files/View.php

Lines 560 to 571 in e66e8ba

	if (!$result) {
	// If create file fails because of permissions on external storage like SMB folders,
	// check file exists and return false if not.
	if (!$this->file_exists($path)) {
	return false;
	}
	if (is_null($mtime)) {
	$mtime = time();
	}
	//if native touch fails, we emulate it by changing the mtime in the cache
	$this->putFileInfo($path, ['mtime' => floor($mtime)]);
	}

[artonge]

CI failure is unrelated

[artonge]

/backport to stable27

[artonge]

/backport to stable26