ceph: fix exec output
ceph: fix exec output

The previous code was overriding the content of `out`, now we just
return after the error.

Signed-off-by: Sébastien Han <62d754cc350e84d3b1c32ae79f976f5348e74a40@redhat.com>

rook/nfs,rook/rook,rook/rook,rook/nfs,rook/rook,rook/rook,rook/rook,rook/nfs