selinux: increase the deprecation sleep for checkreqprot and runtime disable

Further the checkreqprot and runtime disable deprecation efforts by
increasing the sleep time from 5 to 15 seconds to help make this more
noticeable for any users who are still using these knobs.

Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>