chore: refine containers ready condition during image rolling update

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 23.52941% with 13 lines in your changes missing coverage. Please review.

Project coverage is 61.39%. Comparing base (928f3f2) to head (45800e9). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/controller/instanceset/reconciler_update.go	11.11%	6 Missing and 2 partials :warning:
pkg/controller/instanceset/instance_util.go	37.50%	3 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #8429 +/- ## ========================================== + Coverage 61.32% 61.39% +0.07% ========================================== Files 351 351 Lines 41727 41743 +16 ========================================== + Hits 25590 25630 +40 + Misses 13822 13814 -8 + Partials 2315 2299 -16 ``` | [Flag](https://app.codecov.io/gh/apecloud/kubeblocks/pull/8429/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apecloud) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/apecloud/kubeblocks/pull/8429/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apecloud) | `61.39% <23.52%> (+0.07%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apecloud#carryforward-flags-in-the-pull-request-comment) to find out more.

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