and return a single error value EEXIST. When making a recursive
call (to load required modules), treat a pre-existing module as
success.
Without this change, when a module was loaded by specific request
(as opposed to being loaded as a requirement of some other module),
we would always load the module from the file-system, and then
after making various sanity/compatability checks we would destroy
the new copy if there was a pre-existing copy.
Fixes PR kern/40764
XXX Note that if the module exists, we bypass all of the various
XXX "compatability" checks, including whether or not the existing
XXX module is of any particular class! (In the previous code, we
XXX checked to see if the newly-loaded copy had the correct class,
XXX but not the pre-existing copy, which could have been loaded
XXX from a different path/filename.)