DFLYCLUSTER CONFIG command mutex removing

Problem: To avoid several simultaneous CONFIG commands, we use mutex set_config_mu for the whole command execution. Such an approach can create a deadlock like in https://github.com/dragonflydb/dragonfly/issues/4663

We need to remove this mutex according to https://docs.google.com/document/d/1Qptda4qI1ukb4CFWnXGAqoNrmSdhhOLl-OQjiDdKyoM/edit?pli=1&tab=t.0#heading=h.nrnfbp9yix8i