Add functionality to create Salt keypairs

Create Salt key pair if needed
Move Salt key pair creation above bootstrap_server
Pre-seed Salt Minion keys
Use fqdn instead of cert name.
Set the Minion ID to be the fqdn
Logic improvements in add_salt_keypair
Use proper splitext, some suggested fixes
Remove minion_id definition. Let fqdn define minion id

Change-Id: I74e5ffb1a414ee61f1214332be34b5ed0fd26e95
Reviewed-on: https://review.openstack.org/26046
Reviewed-by: James E. Blair <corvus@inaugust.com>
Reviewed-by: Nicolas Simonds <nic@metacloud.com>
Reviewed-by: Anita Kuno <anita.kuno@enovance.com>
Reviewed-by: Matthew Sherborne <msherborne+openstack@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins