Relay log read fail, relay or master log currupt ,How to repair?
After searching for sometime I found a reason and solution.

By default the relay_log_purge variable was on and the relay_log_recovery was off in mysql configuration and both values are default.
As per the mysql documentation the --relay-log-recovery option must be enabled on the slave to guarantee resilience in the event of an unexpected server halt.
so in my case due to no disk space server restarted and relay log corrupt error message came now 

SOLUTION:

first remove the node from group 

do this on the removed slave node

STOP GROUP REPLICATION

RESET SLAVE 

rejoin node to the cluster .It will work.

Explanation:
RESET SLAVE makes the slave forget its replication position in the master's binary log
deletes all the relay log files, and starts a new relay log file.

To use RESET SLAVE on a Group Replication group member, the member status must be OFFLINE, meaning that the plugin is loaded but the member does not currently belong to any group. A group member can be taken offline by using a STOP GROUP REPLICATION statement

For a server where GTIDs are in use (gtid_mode is ON), issuing RESET SLAVE has no effect on the GTID execution history. The statement does not change the values of gtid_executed or gtid_purged