Compare auth version only if ping is successful

[nklaassen]

In lib/service/(*TeleportProcess).reconnectToAuthService we send a ping request to the auth server to check for connectivity. We also check the reported version of the auth server, and will return an error and exit if it is too old.

There is currently a bug where we will check the server version before checking if the ping request was successful, resulting in the following error:

"error":" is not in dotted-tri format","level":"warning","message":"Teleport process has exited with error."

This error causes us to break out of the reconnect loop and never successfully connect to the auth service if there is a single failed ping. This breaks CA rotation if you get unlucky with the timing of auth and proxy restarts.

With this PR, we only check the auth server version if the ping was actually successful.

Fixing the version check uncovered a segfault waiting to happen a few lines below when the error is still nil, this is fixed in the second commit here.

In my testing, this change improved the original pass rate of TestHSMRotation from 94/100 (with 5/6 failures hitting this bug), to 99/100 with the 1 failure being the segfault fixed in the second commit here, to 100/100 999/1000 in the current iteration.

[capnspacehook]

LGTM, sorry about introducing this in the first place 😬

[github-actions]

@nklaassen See the table below for backport results.

Branch	Result
branch/v10	Create PR