Fix user example playbooks that manage certificate members.

These playbooks manage the certificates of a user, but did not have
the proper action for it.

playbooks/user/user_certificate_absent.yml

@@ -9,6 +9,7 @@
     ipauser:
       ipaadmin_password: SomeADMINpassword
       name: test
+      action: member
       certificate:
         - >
           MIIC/zCCAeegAwIBAgIUZGHLaSYg1myp6EI4VGWSC27vOrswDQYJKoZ

playbooks/user/user_certificate_present.yml

@@ -9,6 +9,7 @@
     ipauser:
       ipaadmin_password: SomeADMINpassword
       name: test
+      action: member
       certificate:
         - >
           MIIC/zCCAeegAwIBAgIUZGHLaSYg1myp6EI4VGWSC27vOrswDQYJKoZ