Wrapping GrpcStore with FastSlowStore failure for AC

[chrisstaite-menlo]

Now that GrpcStore supports forwarding to an upstream AcServer, I attempted wrapping it in a FastSlowStore to make a local cache and am getting the following error:

[2023-07-17T08:06:26.568Z ERROR ac_server] get_action_result Resp: 0.14148201 Some("0f3c5b706e843dc5323f8a21ed8ea59bd8d55c53310abf8b11471f0e1e95924c") Err(Error { code: Internal, messages: ["Action result not found", "Failed to get_part in get_part_unchunked", "---", "Writer was dropped before EOF was sent", "Failed to recv first chunk in collect_all_with_size_hint", "Failed to read stream to completion in get_part_unchunked"] })

This is obviously not as expected, so something is wrong with the implementation. I haven't dug into what's causing it yet.

[chrisstaite-menlo]

Digging into this a little, I think it's dumping a horrible error just because the ActionResult wasn't found in the ActionCache. So we just need to catch the error rather than print it I think...

[chrisstaite-menlo]

Furthermore, I think this is simply caused by the removal of the Error from the response of get_action_result_from_digest in get_action_result_as_part from the call to ok() for no apparent reason...