tests/test-debugrename.t

tests: don't run couple of tests related to extensions loading with chg

The couple of files test extensions loading and debugging that. It sets
`devel.debug.extensions` to True to do that.
Either we have to restart chg if this config is set or just don't run these
tests on chg. I tried the first way by adding the config option to chgserver.py
list of config subsections but that does not seem to work.

  $ hg init
  $ echo a > a
  $ hg ci -Am t
  adding a

  $ hg mv a b
  $ hg ci -Am t1
  $ hg debugrename b
  b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3

  $ hg mv b a
  $ hg ci -Am t2
  $ hg debugrename a
  a renamed from b:37d9b5d994eab34eda9c16b195ace52c7b129980

  $ hg debugrename --rev 1 b
  b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3