Instead of scheduling a shutdown session, set a boolean flag and check
that when scheduling/accepting new sessions and connections. That way
it is a bit more obvious in which state the server is.
Preventing shutdown when there is an auto sync config at startup is
wrong. The auto sync flag might get removed later, in which case
shutting down the server becomes okay again. The auto sync manager
must take the shutdown lock as needed. Somehow that worked before,
despite the "m_autoSync.preventTerm() ? -1 : duration".
A test for this will be committed separately.
Instead of coupling different modules directly to each other via
method calls or callbacks, this commit introduces signals which are
connected to methods as necessary when combining the different modules
in the server.
