CRAS: system state - Use shm for server state.
CRAS: system state - Use shm for server state.

Move the server state to shared memory to ease sharing it with clients.
Currently copies of this data are sent to client through ipc.  Sharing a
read-only copy with them will save storage on their end, make messages
smaller, and reduce code complexity on the client side.

BUG=chromium-os32347
TEST=shm_unittest

Change-Id: Ib4bff51025d8144566c908c0dc8fff2aaefcc48c
Signed-off-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/29859
Reviewed-by: Olof Johansson <13dc431ca3b0f062f888def8f8ec4662ec608f7d@chromium.org>

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