Provide mc-admin-heal command on start-up (#4031)
Provide mc-admin-heal command on start-up (#4031)

Healing of buckets, objects and incomplete uploads are implemented and
available via admin REST APIs. Additionally, it is available via mc admin 
sub-command. The warning is no longer relevant.

Fixes #4030
aead/minio,aead/minio,abperiasamy/minio,vadmeste/minio,hackintoshrao/minio,krishnasrinivas/minio,aead/minio,vadmeste/minio,brendanashworth/minio,fwessels/minio,aead/minio,krisis/minio,luomeiqin/minio,abperiasamy/minio,harshavardhana/minio,aead/minio,aead/minio,luomeiqin/minio,minio/minio,rushenn/minio,jimjag/minio,luomeiqin/minio,abperiasamy/minio,rushenn/minio,krisis/minio,aead/minio,jimjag/minio,harshavardhana/minio,luomeiqin/minio,krishnasrinivas/minio,harshavardhana/minio,rushenn/minio,dutchcoders/minio,krishnasrinivas/minio,hackintoshrao/minio,dvstate/minio,harshavardhana/minio,donatello/minio,dvstate/minio,dvstate/minio,dvstate/minio,fwessels/minio,harshavardhana/minio,dutchcoders/minio,rushenn/minio,harshavardhana/minio,hackintoshrao/minio,fwessels/minio,balamurugana/minio,harshavardhana/minio,krishnasrinivas/minio,brendanashworth/minio,brendanashworth/minio,harshavardhana/minio,hackintoshrao/minio,dutchcoders/minio,donatello/minio,fwessels/minio,abperiasamy/minio,dutchcoders/minio,minio/minio,balamurugana/minio,brendanashworth/minio,jimjag/minio,aead/minio,NitishT/minio,jimjag/minio,NitishT/minio,NitishT/minio,NitishT/minio