The observed generation was set to always 0 in #16429, but this had the
knock-on effect of other controllers considering ProxyGroups never ready
because the observed generation is never up to date in
proxyGroupCondition. Make sure the ProxyGroupAvailable function does not
requires the observed generation to be up to date, and add testing
coverage to catch regressions.
Updates #16327
Change-Id: I42f50ad47dd81cc2d3c3ce2cd7b252160bb58e40
Signed-off-by: Tom Proctor <tomhjp@users.noreply.github.com>