release-20.2: kvserver: remove extraneous circuit breaker check in Raft transport

[tbg]

Backport 1/1 commits from #69405.

/cc @cockroachdb/release

---

See #68419. We now use
DialNoBreaker for the raft transport, taking into account the previous
Ready() check.

DialNoBreaker was previously bypassing the breaker as it ought to but
was also not reporting to the breaker the result of the operation;
this is not ideal and was caught by the tests. This commit changes
DialNoBreaker to report the result (i.e. fail or success).

Release justification: bug fix
Release note (bug fix): Previously, after a temporary node outage, other
nodes in the cluster could fail to connect to the restarted node due to
their circuit breakers not resetting. This would manifest in the logs
via messages "unable to dial nXX: breaker open", where XX is the ID
of the restarted node. (Note that such errors are expected for nodes
that are truly unreachable, and may still occur around the time of
the restart, but for no longer than a few seconds).

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[tbg]

@erikgrinaker approved #70349, which is code-identical.