ovirt-foreign-menu: Plug memory leak
    
    Error caught by valgrind, the OvirtCollection object created in function
    ovirt_foreign_menu_fetch_vm_async() was never freed.
    
    433 (40 direct, 393 indirect) bytes in 1 blocks are definitely lost in loss record 16,708 of 17,677
       at 0x5868FDF: g_type_create_instance (in /usr/lib64/libgobject-2.0.so.0.6000.6)
       by 0x584B42C: ??? (in /usr/lib64/libgobject-2.0.so.0.6000.6)
       by 0x584D347: g_object_new_valist (in /usr/lib64/libgobject-2.0.so.0.6000.6)
       by 0x584D69C: g_object_new (in /usr/lib64/libgobject-2.0.so.0.6000.6)
       by 0x558E823: ovirt_collection_new (ovirt-collection.c:304)
       by 0x558E98C: ovirt_sub_collection_new_from_resource_search (ovirt-collection.c:375)
       by 0x42D510: ovirt_foreign_menu_fetch_vm_async (ovirt-foreign-menu.c:994)
       by 0x42D510: ovirt_foreign_menu_next_async_step (ovirt-foreign-menu.c:316)
       by 0x42D70D: api_fetched_cb (ovirt-foreign-menu.c:1025)
       by 0x570BC19: ??? (in /usr/lib64/libgio-2.0.so.0.6000.6)
       by 0x570C7EC: ??? (in /usr/lib64/libgio-2.0.so.0.6000.6)
       by 0x559005D: call_async_cb (ovirt-proxy.c:279)
       by 0x55B5A07: ??? (in /usr/lib64/librest-0.7.so.0.0.0)
    
    Signed-off-by: Eduardo Lima (Etrunko) <etrunko@redhat.com>
    Acked-by: Victor Toso <victortoso@redhat.com>