[calendar-server] Update views only after the time range is set

Moving this from bugzilla: https://bugzilla.gnome.org/show_bug.cgi?id=791464

The gnome-shell-calendar-server calls to refresh queries even when it has not time range set, which results in: a) waste of resources (for example after login), b) many runtime warnings in the journalctl log, related to incorrect time range being used.