Reduce log level of Fernet key count message
Reduce log level of Fernet key count message

This reduces the log level of the fairly repetitive message regarding
the number of Fernet keys on disk, and also adds a suggestion into the
message itself about how the message can be resolved (hint: start
rotating your keys!).

Change-Id: Id35f781c7b34463c324a867c6a781572f4144311
Closes-Bug: 1615111

openstack/keystone,mahak/keystone,mahak/keystone,ilay09/keystone,ilay09/keystone,rajalokan/keystone,ilay09/keystone,rajalokan/keystone,openstack/keystone,openstack/keystone,rajalokan/keystone,mahak/keystone