Make sure that each logical monitor owns the expected actual monitors.
This currently needs special care when dealing with laptop lid the
configuration, as the MetaMonitorConfigManager path still deosn't
handle restoring the previous configuration, meaning the logical
monitor with the external monitor will continue being primary.
https://bugzilla.gnome.org/show_bug.cgi?id=777732
Both the monitor unit tests and monitor store unit tests will want to
check whether the config manager is used and set custom configuration
files.
https://bugzilla.gnome.org/show_bug.cgi?id=777732
