gather-ceph-logs: fix logs list generation

gather-ceph-logs: fix logs list generation

The shell module doesn't have a stdout_lines attributes. Instead of
using the shell module, we can use the find modules.

Also adding `become: false` to the local tmp directory creation
otherwise we won't have enough right to fetch the files into this
directory.

Resolves: #3966

Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>
(cherry picked from commit ea1f8f551cafd3dcd23435630d231811d8cb0e15)