client: don't try to generate keys

client: don't try to generate keys

the entrypoint to generate users keyring is `ceph-authtool`, therefore,
it can expand the `$(ceph-authtool --gen-print-key)` inside the
container. Users must generate a keyring themselves.
This commit also adds a check to ensure keyring are properly filled when
`user_config: true`.

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>
(cherry picked from commit ab1dd3027a4b9932e58f28b86ab46979eb1f1682)
Signed-off-by: Sébastien Han <seb@redhat.com>