Allow instance resize on same host

In v4.2.x, allow_resize_to_same_host defaults to True so that in resource
constrained installations, a resize can happen on the existing host if
there are enough resources there to do it.

- Change allow_resize_to_same_host to True to prevent resize regression in
  9.0.0

Fixes rcbops/ansible-lxc-rpc#104
Merge pull request #106 from claco/issue-104

Allow instance resize on same host