cache: avoid warming the fnodetags cache after clone
That cache can quite expensive to compute on large repository as not that `hg
clone` is warming all cache, this can introduces a significant slowdown for
clone time[1]. As a stop gap measure introduce a quick fix for
that on stable, skipping the fnodetags cache post-clone.
[1] https://www.mercurial-scm.org/pipermail/mercurial/2021-April/052679.html
Differential Revision: https://phab.mercurial-scm.org/D10695
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.