Improve Available Condition

[dthomson25]

Make available condition more clear for BlueGreen and Canary.

A BlueGreen rollout is available when the replicaset that is receiving traffic from the active selector has the min availability of pods.

A Canary Rollout is available when the sum of available pods from all replicasets is greater than or equal to the rollout's replica count.

Note: Before this PR, the HPA selector in the status wasn't being updated when the activeSelector was switched. That was okay previously because the controller would have enqueued the rollout again and change the HPA selector on the second reconciliation. Part of this implementation includes the selector change in the first reconciliation.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@ce5920c). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master      #60   +/-   ##
=========================================
  Coverage          ?   78.27%           
=========================================
  Files             ?       14           
  Lines             ?     1625           
  Branches          ?        0           
=========================================
  Hits              ?     1272           
  Misses            ?      266           
  Partials          ?       87

Impacted Files	Coverage Δ
controller/service.go	84.88% <ø> (ø)
utils/conditions/conditions.go	89.11% <ø> (ø)
controller/bluegreen.go	81.33% <100%> (ø)
controller/sync.go	74.08% <100%> (ø)
utils/replicaset/replicaset.go	94.3% <100%> (ø)

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[alexmt]

Looks good!