Reduce log level of failure to publish report to DB

[awygle]

Soundtrack of this PR: The Impressions - It's All Right

Motivation

Bringing forward changes which were in progress before moving the fog repo to the unified repo.

In this PR

• Reduce log level of failure to publish report to DB

Context from [mobilecoinfoundation/fog#147]:

Sometimes, we lose connection to the sql DB, and the report server write operation fails.

This should not be logged as an error because it's not actionable and errors get converted to sentry alerts.

Fixes [mobilecoinfoundation/fog#147] and [#1892].

[iamalwaysuncomfortable]

I think removing the comment PublishError catch in favor of a shorter comment above the catch (which would be more rust-idiomatic) would be the simplest way to improve the PR.

A more elegant way might be to split the publisher error in the PR into two more contextual errors and do the log::warn! about the publisher error within the Error::PublishReport branch of the error.

Something to the tone of:

    /// Incorrect ingress key: {0}
    BadIngressKey(CompressedRistrettoPublic)
    /// Report publication/ingress key checkup failed: {0}
    PublishReport(String),

This more detailed way is entirely optional though as the FOG SLA is improved either way.

[cbeck88]

we should keep sleeping when PublishReport error occurs, as we did before

[iamalwaysuncomfortable]

Bump to @awygle on this - what are your thoughts on how to proceed forward? This is a positive FOG SLA item 🥇 that I think is almost in reach.

Addressed in subsequent commit.