Return the session manager mock from its fixture, not a dummy object
Return the session manager mock from its fixture, not a dummy object

The mock session doesn't get used by the tests themselves, just by the
fixture's setup and its teardown, but it may be interesting to use it
later to frob the session's state.

GNOME/at-spi2-core,GNOME/at-spi2-core,GNOME/at-spi2-core