Add support for update order

This parameter controls the order of operations when rolling out an
update task. Either the old task is stopped before starting the new one,
or the new task is started first, and the running tasks will briefly
overlap.

This commit adds Rollout to the API, and --update-order / --rollback-order
flags to the CLI.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

docs/reference/commandline/service_create.md

@@ -65,6 +65,7 @@ Options:
       --rollback-max-failure-ratio float   Failure rate to tolerate during a rollback
       --rollback-monitor duration          Duration after each task rollback to monitor for failure
                                            (ns|us|ms|s|m|h) (default 0s)
+      --rollback-order string              Rollback order ("start-first"|"stop-first") (default "stop-first")
       --rollback-parallelism uint          Maximum number of tasks rolled back simultaneously (0 to roll
                                            back all at once) (default 1)
       --secret secret                      Specify secrets to expose to the service
@@ -75,6 +76,7 @@ Options:
       --update-failure-action string       Action on update failure ("pause"|"continue"|"rollback") (default "pause")
       --update-max-failure-ratio float     Failure rate to tolerate during an update
       --update-monitor duration            Duration after each task update to monitor for failure (ns|us|ms|s|m|h)
+      --update-order string                Update order ("start-first"|"stop-first") (default "stop-first")
       --update-parallelism uint            Maximum number of tasks updated simultaneously (0 to update all at once) (default 1)
   -u, --user string                        Username or UID (format: <name|uid>[:<group|gid>])
       --with-registry-auth                 Send registry authentication details to swarm agents

docs/reference/commandline/service_update.md

@@ -77,6 +77,7 @@ Options:
       --rollback-max-failure-ratio float   Failure rate to tolerate during a rollback
       --rollback-monitor duration          Duration after each task rollback to monitor for failure
                                            (ns|us|ms|s|m|h) (default 0s)
+      --rollback-order string              Rollback order ("start-first"|"stop-first") (default "stop-first")
       --rollback-parallelism uint          Maximum number of tasks rolled back simultaneously (0 to roll
                                            back all at once) (default 1)
       --secret-add secret                  Add or update a secret on a service
@@ -88,6 +89,7 @@ Options:
       --update-failure-action string       Action on update failure ("pause"|"continue"|"rollback") (default "pause")
       --update-max-failure-ratio float     Failure rate to tolerate during an update
       --update-monitor duration            Duration after each task update to monitor for failure (ns|us|ms|s|m|h) 
+      --update-order string                Update order ("start-first"|"stop-first") (default "stop-first")
       --update-parallelism uint            Maximum number of tasks updated simultaneously (0 to update all at once) (default 1)
   -u, --user string                        Username or UID (format: <name|uid>[:<group|gid>])
       --with-registry-auth                 Send registry authentication details to swarm agents