Honor metadata etag for get_certs path.

[adepue]

Description

Issue #

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PR information

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[adepue]

@narrieta for feedback

[narrieta]

Change looks ok. Running automation.

[adepue]

@narrieta Seems that the etag value wasn't ever being passed up to the server either. I have added another commit here that addresses that. Let me know what you think.

[adepue]

The entire restutil class here doesnt seem to honor the 304 response codes per the protocol. I am going to close this PR for now and will bring it back once we have fully verified the failure patterns. Sorry for the scramble @narrieta

[narrieta]

@adepue No problem, thanks!

[adepue]

@narrieta I have updated to incorporate handling of 304 return codes in a way isolated to the metadata protocol only. Let me know what you think of the code structure. We have a setup we can test on once we are fine with the code approach.

[adepue]

@narrieta Let me know if you have concerns with this approach/update at all.

[narrieta]

Looks good. Running automation