On Linux it seems common that the TZ variable is NOT properly set.
There are some concerns that the warning related to rsyslog correcting
this confuses users. It also seems that the corrective action rsyslog
takes is right, and so there is no hard need to inform users on that.
In Linux containers, however, the warning seems to be useful as the
timezone setup there seems to be frequently-enough different and
rsyslog's corrective action may not be correct.
So we now check if we are running under Linux and not within a container.
If so, we do not emit the warning. In all other case, we do. This is
based on the assumption that other unixoid systems still should have
TZ properly set.
closes https://github.com/rsyslog/rsyslog/issues/2994
502759aea0