tasks/ceph: add ceph.stop task

So that we can explicitly stop daemons on demand.  Useful
for MDS tool tests that want the MDS daemons not to be running,
is this is more solid and explicit than doing e.g. "ceph mds
stop" from within workunits.

Signed-off-by: John Spray <john.spray@redhat.com>
tasks/workunit: fix log message

Signed-off-by: John Spray <john.spray@redhat.com>
tasks/ceph_fuse: enable umounting from config

This is for any test config that needs to run
some workunit with clients unmounted.  It allows
you to go toggle the mountedness of a client as
you go up and down the stack list this:

- ceph-fuse:
    client.0:
        mounted: true
- workunit:
    clients:
        client.0:
        - fs/misc/trivial_sync.sh
- ceph-fuse:
    client.0:
        mounted:
            false

The initial use case for this is running the
cephfs_journal_tool_smoke.sh workunit, which
tests administrative operations that are meant
to be run on an unmounted filesystem.

Signed-off-by: John Spray <john.spray@redhat.com>
tasks/mds_client_recovery: network freeze test

This is about testing the CephFS client's handling
of losing connectivity to the MDS.

Fixes: #7810

Signed-off-by: John Spray <john.spray@redhat.com>
tasks/mds_client_recovery: use existing clients

This will enable using .yaml changes to switch this
guy over to use kcephfs client once the teuthology
code around it supports all the same hooks as I've added
for fuse.

Signed-off-by: John Spray <john.spray@redhat.com>
suites/fs: add client recovery

Signed-off-by: John Spray <john.spray@redhat.com>
gitignore: ignore vim temp files

Signed-off-by: John Spray <john.spray@redhat.com>
suites/fs: add cephfs_journal_tool test

Fixes: #4886

Signed-off-by: John Spray <john.spray@redhat.com>