core: Make load_module multiple invocation safe
core: Make load_module multiple invocation safe

If the module is already loaded then skip that module.

ThomasBollmeier/libsocialweb-flickr-oauth,lcp/libsocialweb,lcp/libsocialweb,GNOME/libsocialweb,GNOME/libsocialweb,GNOME/libsocialweb,ThomasBollmeier/libsocialweb-flickr-oauth,ThomasBollmeier/libsocialweb-flickr-oauth,lcp/libsocialweb