mgr/orch: try harder when pickle fails to marshal an exception

mgr/orch: try harder when pickle fails to marshal an exception

pickle cannot marshal instances of class not defined in the top level of
a module. for instance, `DriveGroupValidationError` is defined in a
submodule of `ceph` python module, that's why we cannot capture it.

this prevent the `ceph` command line from getting a proper error when
the command fails if the command is implemented using cross python
module call(s).

Signed-off-by: Kefu Chai <kchai@redhat.com>