repoview: make propertycache.setcache compatible with repoview Propertycache used standard attribute assignment. In the repoview case, this assignment was forwarded to the unfiltered repo. This result in: (1) unfiltered repo got a potentially wrong cache value, (2) repoview never reused the cached value. This patch replaces the standard attribute assignment by an assignment to `objc.__dict__` which will bypass the `repoview.__setattr__`. This will not affects other `propertycache` users and it is actually closer to the semantic we need. The interaction of `propertycache` and `repoview` are now tested in a python test file.

Test issue2761

  $ hg init

  $ touch to-be-deleted
  $ hg add
  adding to-be-deleted
  $ hg ci -m first
  $ echo a > to-be-deleted
  $ hg ci -m second
  $ rm to-be-deleted
  $ hg diff -r 0

Same issue, different code path

  $ hg up -C
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ touch does-not-exist-in-1
  $ hg add
  adding does-not-exist-in-1
  $ hg ci -m third
  $ rm does-not-exist-in-1
  $ hg diff -r 1