Change VADB role to server.

This change also introduces a master event loop, which allows us to drop
threads and mutexes. This also detaches us from QEmu lifecycle, making
it possible to accept connection whenever QEmu is ready.

With the series of these changes in, QEmu will require VirtualADB to be
ready before it can boot up.

Change-Id: If749b224c3f2f0ab449005f54988fa9f354b2244
(cherry picked from commit 703e36ea2e02543bc8fc5c022f1fe2a2fe619a36)
10 files changed