Whitespace is not removed from the end of the stdout returned by the
method get_ceph_cmd_stdout(). Follow the same policy here since it is
better to not do so (this whitespace can be useful, when copying Ceph
auth keyrings from stdout to a file) and also for sake of uniformity of
interfaces.

Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit 9582b9b)

Conflicts:
qa/tasks/cephfs/mount.py
- Method get_shell_stdout() was absent in mount.py, it has been added
  now in this very commit since it future commit from this PR need it.

Setting MGR config option mgr/volumes/pause_purging to true halts
all ongoing purges and allows no new purging to begin until this option
is changed to false. Add tests for this.

Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit f38fcbc)

Conflicts:
qa/tasks/cephfs/test_volumes.py
- safe_while was already needed to be import on main branch but it is
  not in Squid branch which lead to the conflict. It has been imported
  now through this commit since tests in it need it.
- Some test methods right next to new test added by this commit are
  absent in Squid compared to main branch which lead

Trash directory for a volume is not created by default. If
_wait_for_trash_empty() in test_volumes.py encounters absence of trash
directory, return true.

Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit 6d6be8b)

mgr/vol config option pause_cloning allows pausing of cloner threads.
Add tests for this.

Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit e7eb36e)

Update documentation for add information about mgr/vol config options
"pause_purging" and "pause_cloning".

Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit 1f0bfe1)

Added release notes for mgr/vol config option "pause_purging and
"pause_cloning".

Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit 03b90d5)