Cleanup of Zygote files

This CL cleans up some warnings in the ZygoteInit.java and
ZygoteServer.java files.  These warnings were mostly about unused
variables, protection class changes, and dead code.  Some changes
to code in Zygote.java and ZygoteConnection.java were needed due to
function signature changes.

Test: Built and booted image
Change-Id: I6ba33cfcb4729a75dbbd4f908f4b46110d3bb991