SetConfigHandler should avoid setting an invalid notification config (#6679)
SetConfigHandler should avoid setting an invalid notification config (#6679)

Fixes #6642 
Fixes #6641
harshavardhana/minio,NitishT/minio,jimjag/minio,harshavardhana/minio,balamurugana/minio,jimjag/minio,krisis/minio,NitishT/minio,krisis/minio,balamurugana/minio,aead/minio,krishnasrinivas/minio,fwessels/minio,aead/minio,vadmeste/minio,harshavardhana/minio,harshavardhana/minio,minio/minio,jimjag/minio,harshavardhana/minio,harshavardhana/minio,minio/minio,fwessels/minio,donatello/minio,fwessels/minio,aead/minio,fwessels/minio,krishnasrinivas/minio,aead/minio,NitishT/minio,krishnasrinivas/minio,NitishT/minio,aead/minio,donatello/minio,vadmeste/minio,jimjag/minio,aead/minio,krishnasrinivas/minio,aead/minio,harshavardhana/minio,aead/minio,harshavardhana/minio