Floss: add MMC DBus service daemon and related conf files.

In this patch, MMC DBus service daemon will be invoked when DBus method
|CodecInit| or |CodecCleanUp| is called. In |CodecInit|, the daemon
creates a socket and makes a worker thread listen on the socket. In
|CodecCleanUp|, the daemon shuts down all idle threads. Configuration
files are added to set up daemon priveldges and DBus startup.

Bug: 294165109
Tag: #floss
Test: m - None
Change-Id: Ied3b142a006797bc2a922ea9f091d6c187f84bd0