Increase unit test coverage in the ocdav service

[butonic]

Description

The ocdav service serves our most fundamental APIs: /webav, /dav/files, /dav/spaces, /dav/files-public...

But currently we are at 3.1%

Running tool: /usr/local/bin/go test -timeout 30s -coverprofile=/tmp/vscode-goeLSGxw/go-code-cover github.com/cs3org/reva/v2/internal/http/services/owncloud/ocdav

ok  	github.com/cs3org/reva/v2/internal/http/services/owncloud/ocdav	0.027s	coverage: 3.1% of statements

Goal: bring coverage up to 70%

[stale]

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