Remove uses of libcore.io DropBox and EventLogger

DropBox and EventLogger provide hooks for use by framework to intercept
messages sent by libcore. However, neither of these mechanisms are
actually used by libcore so there is no point in framework code using
it.

Bug: 119748341
Test: make checkbuild, flash
Change-Id: I9dbd1b6dea92f7441efb6d0a579efd13bc0e5139