healObject() should be non-blocking to ensure
that scanner is not blocked for a long time,
this adversely affects performance of the scanner
and also affects the way usage is updated
subsequently.
This PR allows for a non-blocking behavior for
healing, dropping operations that cannot be queued
anymore.
This is to ensure that there are no projects
that try to import `minio/minio/pkg` into
their own repo. Any such common packages should
go to `https://github.com/minio/pkg`