correctly maintain connecting state and connection icons
m_connecting is not always maintained correctly, thus it causes some problem on plasmoid side. In the old code, if there are multiple connections, activeConnectionDestroy might set connecting to wrong value if there's another connection connecting.
This patch introduce ConnectionIcon::setStates() function, which always scan through all active connections (number of active connections is relatively small so it won't affect performance), and set connecting to true if any connection is in "Activtating" state.