libmodprobe: Do not reload modules previously instantiated

For modprobe operation.

For an interlocking driver set of about 50 modules, the impact of
their dependencies resulted in a 30 second impact in boot time
trying to load previously loaded modules. This impact is handily
eliminated by keeping a list of modules paths that have been loaded
and skipping them proactively.

Test: Confirmed device boot and 50 module set of drivers functions.
Test: libmodprobe_tests
Bug: 142938937
Bug: 140827934
Change-Id: Iccd11399d6043b38cbd5f93578ee202022e7770c