func: clean the module cache on first load error

In case if we're loading a fresh module we put it
into a module's cache first which allows us to not
reload same module twice (say there could be several
functions in same module).

But if the module is loaded for the first time and
symbol resolution failed we continue keeping this
module loaded even if there may be no more use of
it. Thus make a cleanup if needed.

There is no portable way to verify via test as far
as I know, just manually via "lsof -p `pidof tarantool`".

Fixes #5475

Reported-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>