lib/module: check initstate before inserting module

lib/module: check initstate before inserting module

This applies to both the high level probe_insert_module() and the
underlying insert_module() functions. By checking module initstate prior
to inserting a module, we can avoid a lot of needless work just to find
out that the init_module call fails with EEXIST.

This implements a helper function, module_is_inkernel, to return a
boolean value describing if a module is live, coming, or builtin.