phabricator: pass ui into readurltoken instead of passing repo
The goal of this series is to make `hg debugcallconduit` work outside of a hg
repo.
This patch, removes requirement of repo object from readurltoken as we only need
ui there. It also updates the callers to pass in ui instead of repo.
Differential Revision: https://phab.mercurial-scm.org/D6497