Enhance the service manager status after WSREP state transfer.

Hello,

This is a follow-up request regarding MDEV-35969.

Currently, after completing the WSREP state transfer, we are updating the status information of the systemd service as follows:

$ grep -n sd_notify ./sql/wsrep_sst.cc

146:  sd_notify(0, "STATUS=WSREP state transfer (role donor) completed.\n");

184:  sd_notify(0, "STATUS=WSREP state transfer (role joiner) completed.\n");

Can we enhance the status information to "WSREP state transfer (xxx) completed. Taking SQL requests again." so that the users could clearly understand the cluster's state?

Thank you.

Best regards,
Flos