Current master has a regression 'mc policy <policy-type> alias/bucket/prefix'
does not work anymore, due to the way new minio-go changes do json marshalling.
This led to a regression on server side when a ``prefix`` is provided
policy is rejected as malformed from th server which is not the case with
AWS S3.
This patch uses the new ``minio-go/pkg/set`` package to address the
unmarshalling problems.
Fixes#2503
Policies are read once during server startup and subsequently
managed through in memory map. In-memory map is updated as
and when there are new changes coming in.
* Added ErrPolicyNesting which is returned when nesting of policies has occured
* Replaces ErrMalformedPolicy in the case of nesting
* Changed test case in bucket-policy-parser_test.go (ErrMalformedPolicy -> ErrPolicyNesting)
Harshavardhana