discoverd/cache: Replay full Instance structs
discoverd/cache: Replay full Instance structs

Some watchers may want to refer to instance metadata, which was
previously missing when generating the "current" events.

Signed-off-by: Lewis Marshall <748e1641a368164906d4a0c0e3965345453dcc93@lmars.net>

philiplb/flynn,philiplb/flynn,lmars/flynn,philiplb/flynn,flynn/flynn,flynn/flynn,flynn/flynn,lmars/flynn,philiplb/flynn,philiplb/flynn,lmars/flynn,lmars/flynn,flynn/flynn,lmars/flynn,flynn/flynn