Make e_dbus_server_load_modules() idempotent.
Make e_dbus_server_load_modules() idempotent.

The function now keeps a static hash table of module directories it has
loaded, and simply returns if it detects a previously loaded directory.

tintou/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server