don't extra notify ModulesDidLoad() from LoadModuleAtAddress()

Places calling LoadModuleAtAddress() already call ModulesDidLoad()
after a loop calling LoadModuleAtAddress(), so it's not necessary
to call it from there, and the batched ModulesDidLoad() may be
more efficient than this place calling it one after one.

This also makes the ModuleLoadedNotifys test pass on Linux now that
the duplicates no longer bring down the average of modules notified
per call.

Differential Revision: https://reviews.llvm.org/D123128