taskserver: Pass configuration via command line

Putting an include directive in the configuration file referencing a
store path with the real configuration file has the disavantage that
once we change the real configuration file the store path is also a
different one.

So we would have to replace that include directive with the new
configuration file, which is very much error-prone, because whenever
taskd modifies the configuration file on its own it generates a new one
with *only* the key/value options and without any include directives.

Another problem is that we only added the include directive on the first
initalization, so whenever there is *any* configuration change, it won't
affect anything.

We're now passing all the configuration options via command line,
because taskd treats everything in the form of --<name>=<value> to be a
configuration directive.

This also has the effect that we now no longer have extraConfig, because
configuration isn't a file anymore.

Instead we now have an attribute set that is mapped down to
configuration options.

Unfortunately this isn't so easy with the way taskd is configured,
because there is an option called "server" and also other options like
"server.cert", "server.key" and so on, which do not map very well to
attribute sets.

So we have an exception for the "server" option, which is now called
"server.listen", because it specifies the listening address.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Fixes: #22705