Code review comment for lp:~sinzui/launchpad/import-person

This is my branch to fix imports.

    lp:~sinzui/launchpad/import-person
    Diff size: 45
    Launchpad bug: https://bugs.launchpad.net/bugs/import-person
    Test command: ./bin/py -c 'from lp.registry.model
    Pre-implementation: no one. I fixed it as I was triaging the bug
    Target release: 3.1.0

= Fix imports =

./bin/py -c 'from lp.registry.model import person' fails due to circular import

== Rules ==

While trying to understand the scope of the bug I realised the problem was
in one of the unmigrated apps. After I fixed it, I searched for and fixed
all the locations that imported from database.

== Lint ==

Linting changed files:
  lib/canonical/launchpad/database/__init__.py
  lib/canonical/launchpad/doc/hwdb-device-tables.txt
  lib/canonical/launchpad/zcml/launchpadstatistic.zcml

== Test ==

    * lib/canonical/launchpad/doc/hwdb-device-tables.txt
      * Fixed the import in the test.

== Implementation ==

    * lib/canonical/launchpad/database/__init__.py
      * Removed the unneeded import
    * lib/canonical/launchpad/zcml/launchpadstatistic.zcml
      * Fixed the import in ZCML.