In fff4d1ba97f77bbd52d9a48ce4f19b5ed55e40e4 one selection_manager_get
method was patched to behave like this, however, it completly broke the
fact of *only-one-manager* since the same code was duplicated in a other
files (efl_selection.c). This now unifies this code, and adds back the
assertion for only one manager per window.
Additionally a shutdown function is added, the app never destroyes, but
the selection manager decided to init some subsystems itself
(ecore_x for example). This lead to to a leak of init counts in ecore_x,
which lead to elementary test suite issues. This is now *finaly* fixed.
Depends on D7104