will that 6 access point will switchover to failover wlc 2106 above then 20 sec.
If you configure global or AP-level HA (not to be confused with SSO), then yes. When your primary controller fails, the AP will site there waiting for the primary controller to recover for about 20 seconds. Then they will switch to the secondary. When the primary recovers, you have the option to switch back, the AP will join the primary controller again.
During the "delay" to switch over from primary to secondary (and back), any clients connection will fail. Full authentication will occur once the AP has settled into thier respective controller.