infinitepush: use `get_unique_pull_path`
The extension does not support multiple destination (yet).
Differential Revision: https://phab.mercurial-scm.org/D10456
relink: use `get_unique_pull_path`
The code does not support multiple destination and will probably never do so.
So lets use the dedicated API for this case.
Differential Revision: https://phab.mercurial-scm.org/D10409