Add missing read lock around event pushing from value that isn't
required to be cached.

Bug-AGL: SPEC-2880
Change-Id: I7aae2ec9df722fdefcec2d35977251e008375d92
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>

To remove dependency on DBus the binding needed to be rewritten to
output pure JSON output to subscribed consumers.

Bug-AGL: SPEC-2880
Change-Id: Ie85dfccd42ca36119116a0fbfb16bf4e96efc184
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>