Make structure of android directory consistent

All the upstream directories have their code in src/main/java and
src/test/java sub-directories but the locally added android directory
had it in main/java and test/java instead. This change makes the
android directory consistent with upstream.

Bug: 117818301
Test: make checkbuild
Change-Id: Idd8b486bc705edba0ddba657ae38613fb1008e6a