Instruct etcd to delete old revisions

[hedleyroos]

Etcd keeps old revisions unless instructed to delete them. If we don't delete old revisions then etcd memory usage will keep growing forever due to keepalive updates. Since Patroni does not really need to roll back to older revisions we can safely delete them.

[CyberDem0n]

👍

[coveralls]

Pull Request Test Coverage Report for Build 9059959544

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 8 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.001%) to 99.862%

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Files with Coverage Reduction	New Missed Lines	%
patroni/ha.py	2	99.84%
patroni/collections.py	3	94.64%
patroni/psycopg.py	3	78.57%

Totals
Change from base Build 7898066020:	0.001%
Covered Lines:	13760
Relevant Lines:	13779

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💛 - Coveralls

[hughcapet]

👍