contrib: fix generate group_vars samples

For ceph-iscsi-gw and ceph-rbd-mirror roles the group_name are named
differently (by default) than the role name so we have to change the
script to generate the correct name.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1602327
Signed-off-by: Sébastien Han <seb@redhat.com>
(cherry picked from commit 315ab08b16)

generate_group_vars_sample.sh

@@ -66,6 +66,10 @@ for role in "$basedir"/roles/ceph-*; do
     output="agent.yml.sample"
   elif [[ $rolename == "ceph-fetch-keys" ]]; then
     output="ceph-fetch-keys.yml.sample"
+  elif [[ $rolename == "ceph-rbd-mirror" ]]; then
+    output="rbdmirrors.yml.sample"
+  elif [[ $rolename == "ceph-iscsi-gw" ]]; then
+    output="iscsigws.yml.sample"
   else
     output="${rolename:5}s.yml.sample"
   fi