ecore: Reset do_quit when ecore shuts down

After ecore_shutdown the main loop is dead, so the flag do_quit can be
safely reset to 0. This will fix issues with cycles of
elm_init/shutdown. This fixes:
  CK_FORK=no tests/elementary/elm_suite elm_win

This patch relies on a few of the previous patches which ensure that
ecore is well shut down.

@fix

src/lib/ecore/ecore_main.c

@@ -1659,6 +1659,7 @@ _ecore_main_shutdown(void)
    fd_handlers_to_call_current = NULL;
    fd_handlers_to_delete = NULL;
    fd_handler_current = NULL;
+   do_quit = 0;
 
 #ifdef _WIN32
    while (win32_handlers)