fix error during mkcol

[micbar]

Description

We need to return 409 Conflict when one or more path elements during an MKCOL do not exist.

Fixes: owncloud/ocis#6136

[micbar]

@dragotin This is a fix to enable the usage of rclone

[glpatcern]

@redblom do we need this in master or do we already have this behaviour?

[redblom]

@micbar @glpatcern : I can confirm that master returns 409 Conflict and rclone behaves as expected, it can create a complete new path.

[micbar]

@micbar @glpatcern : I can confirm that master returns 409 Conflict and rclone behaves as expected, it can create a complete new path.

@redblom Can you check if this is also the case for non-existing sub-sub directories?

[dragonchaser]

lgtm

[redblom]

@redblom Can you check if this is also the case for non-existing sub-sub directories?

@micbar Yes, also with sub/sub/.. directories, the response is always 409 Conflict (message: Parent node does not exist)