rolling_update: move mgr key creation

rolling_update: move mgr key creation

Until all the mons haven't been updated to Luminous, there is no way to
create a key. So we should do the key creation in the mon role only if
we are not part of an update.
If we are then the key creation is done after the mons upgrade to
Luminous.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1574995
Signed-off-by: Sébastien Han <seb@redhat.com>
(cherry picked from commit 52fc8a0385a7bc58b8b33fc0c5e05db1a03c5c1f)
Signed-off-by: Sébastien Han <seb@redhat.com>