MINOR: checks: Remove useless tests on the connection and conn-stream

During an health check execution, the conn-stream and the conncetion may only be
NULL before the evaluation of the first rule, which is always a connect, or if
the first conn-stream allocation failed. Thus, in tcpcheck_main(), useless tests
on the conn-stream or on the connection have been removed. A comment has been
added to make it clear.

No backport needed.
1 file changed