HOWTO: add description and examples of verify triggers

Signed-off-by: Jens Axboe <axboe@fb.com>
client: defer local trigger execute until after state is received

Don't run it immediately, we have to wait until we receive the
data from the server.

Signed-off-by: Jens Axboe <axboe@fb.com>
trigger: always send trigger, not just when remote command is set

Signed-off-by: Jens Axboe <axboe@fb.com>
server: fix missing ETA in some cases

If we get an ETA request from the client, we pass in 'force' to
ignore any time constraints. But we fail to pass the force through,
so we can fail sending the requested ETA and the client just looks
like nothing is running even though it is.

Signed-off-by: Jens Axboe <axboe@fb.com>