ncm-ceph: fix for cat and ls things

Why?

I see command management is done in `NCM::Component::Ceph::commands`. It should export whatever constants it needs, maybe with a tag, just as it does for `@SSH_COMMAND`.

Say:

```perl
package NCM::Component::Ceph::commands;

use base qw(Exporter);
use Readonly;

Readonly our @CAT_COMMAND => ...;

our %EXPORT_TAGS = (commands => [qw(@CAT_COMMAND @SSH_COMMAND...)];
```
And in the consumers:

```perl
use NCM::Component::Ceph::Commands qw(:commands);

# Use @SSH_COMMAND and @CAT_COMMAND at will.
```