tasks: create mds_flush task

This tests:
 * The new 'flush journal' asok command
 * That the resulting on disk structures are as expected
 * That cephfs-journal-tool is happy with the result

Fixes: #9881

Signed-off-by: John Spray <john.spray@redhat.com>
suites/fs: hook in mds_flush

Signed-off-by: John Spray <john.spray@redhat.com>
Merge pull request #227 from ceph/wip-9881

#9881 MDS flush journal test

Reviewed-by: Greg Farnum <gfarnum@redhat.com>
tasks/ceph_manager: dump raw cluster command at debug level

Signed-off-by: Sage Weil <sage@redhat.com>
Merge pull request #275 from ceph/wip-10404

tasks/ceph_manager: debug raw command output
Revert "tasks/ceph_manager: dump raw cluster command at debug level"

This reverts commit b0ebeba79cf349b9c5a6e387f8246d7b6d0ef576.
Revert "Move output in task/s3readwrite"

This reverts commit 26a33c3a5aa2aedb52eb5ce140c76503f099b253.

This is tryign to create the archive dir on the remote host:

2014-12-29T12:15:30.213 INFO:teuthology.orchestra.run.plana31:Running: 'mkdir -p /var/lib/teuthworker/archive/sage-2014-12-29_11:40:52-rgw-next---basic-multi/683052'
2014-12-29T12:15:30.231 ERROR:teuthology.contextutil:Saw exception from nested tasks
Traceback (most recent call last):
  File "/home/teuthworker/src/teuthology_master/teuthology/contextutil.py", line 28, in nested
    vars.append(enter())
  File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/var/lib/teuthworker/src/ceph-qa-suite_next/tasks/s3readwrite.py", line 241, in run_tests
    ctx.cluster.only(client).run(args=['mkdir', '-p', archive_dir])
  File "/home/teuthworker/src/teuthology_master/teuthology/orchestra/cluster.py", line 64, in run
    return [remote.run(**kwargs) for remote in remotes]
  File "/home/teuthworker/src/teuthology_master/teuthology/orchestra/remote.py", line 128, in run
    r = self._runner(client=self.ssh, name=self.shortname, **kwargs)
  File "/home/teuthworker/src/teuthology_master/teuthology/orchestra/run.py", line 368, in run
    r.wait()
  File "/home/teuthworker/src/teuthology_master/teuthology/orchestra/run.py", line 106, in wait
    exitstatus=status, node=self.hostname)
CommandFailedError: Command failed on plana31 with status 1: 'mkdir -p /var/lib/teuthworker/archive/sage-2014-12-29_11:40:52-rgw-next---basic-multi/683052'

...but it should only be on the local host.