Backport changes from release/2.9

[StephenSorriaux]

Why is this needed?

• bump the version
• update changelog
• backport the fix that overrides the egg_info tag-build configuration

Proposed Changes

• bump version to 2.9.0
• add changelog for 2.9.0
• add some flags to build module to override tag-build value from setup.cfg

Does this PR introduce any breaking change?

No

[codecov-commenter]

Codecov Report

Base: 94.42% // Head: 94.45% // Increases project coverage by +0.02% :tada:

Coverage data is based on head (28ea638) compared to base (bd62797). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #670 +/- ## ========================================== + Coverage 94.42% 94.45% +0.02% ========================================== Files 57 57 Lines 8399 8399 ========================================== + Hits 7931 7933 +2 + Misses 468 466 -2 ``` | [Impacted Files](https://codecov.io/gh/python-zk/kazoo/pull/670?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk) | Coverage Δ | | |---|---|---| | [kazoo/version.py](https://codecov.io/gh/python-zk/kazoo/pull/670/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vdmVyc2lvbi5weQ==) | `100.00% <100.00%> (ø)` | | | [kazoo/tests/test\_client.py](https://codecov.io/gh/python-zk/kazoo/pull/670/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vdGVzdHMvdGVzdF9jbGllbnQucHk=) | `98.70% <0.00%> (-0.10%)` | :arrow_down: | | [kazoo/protocol/connection.py](https://codecov.io/gh/python-zk/kazoo/pull/670/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vcHJvdG9jb2wvY29ubmVjdGlvbi5weQ==) | `96.28% <0.00%> (+0.41%)` | :arrow_up: | | [kazoo/recipe/queue.py](https://codecov.io/gh/python-zk/kazoo/pull/670/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vcmVjaXBlL3F1ZXVlLnB5) | `98.08% <0.00%> (+0.63%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk)

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[StephenSorriaux]

Mh I made a mistake by merging https://github.com/python-zk/kazoo/pull/671 before, because now I don't want to force push to the release/2.9 branch to get those changes back. Will open another PR and cherry-pick.