Handle Xenial which is similar to Trusty and also Focal, where we need
to install Firebird 3.0 server and tweak expect command to work with it.
Note that we still use Xenial for GitHub Actions Firebird CI build as
using Focal version results in memory leaks inside Firebird libraries
and there doesn't seem to be a debug symbol package for Firebird 3.0
that would be required to write a suppression file for them.
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