gnus-cloud: Improve cloud sync

After replaying a set of actions downloaded by gnus-cloud, persist the
highest sequence number seen as the local `gnus-cloud-sequence'
number, in order that a future download will not unnecessarily replay
previously seen actions and any future uploads from this emacs
instance use a higher sequence number than that downloaded.

Remove the test on whether individual newsrc entries are older than
the current time, as that is always going to be the case.
2 jobs for scratch/tzz/dme/bug-40280-gnus-cloud-newest in 80 minutes and 27 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Test
failed #6304
test-all

01:20:27

failed #6305
test-filenotify-gio

00:00:06

 
Name Stage Failure
failed
test-all Test
make[2]: *** [check-doit] Error 1
Makefile:319: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:294: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
make: *** [check-expensive] Error 2
Makefile:959: recipe for target 'check-expensive' failed
ERROR: Job failed: exit code 1
failed
test-filenotify-gio Test There has been a runner system failure, please try again
Running with gitlab-runner 12.0.2 (d0b76032)
on emba-docker-runner 2oEDrUT7
Using Docker executor with image debian:stretch ...
Pulling docker image debian:stretch ...
Using docker image sha256:5738956efb6b994ba2552e96100cc6a6d8a1f0c7dea402bddd54c5cf6f6871f8 for debian:stretch ...
Running on runner-2oEDrUT7-project-1-concurrent-0 via emba.gnu.org...
ERROR: Job failed (system failure): Error response from daemon: No such container: 44db7ec4eb07b9acb369eb9127a9792570c991f8ef65411adfbf1f765f870e7e (executor_docker.go:726:0s)