it is not safe to pass around sync.Map
through pointers, as it may be concurrently
updated by different callers.
this PR simplifies by avoiding sync.Map
altogether, we do not need sync.Map
to keep object->erasureMap association.
This PR fixes a crash when concurrently
using this value when audit logs are
configured.
```
fatal error: concurrent map iteration and map write
goroutine 247651580 [running]:
runtime.throw({0x277a6c1?, 0xc002381400?})
runtime/panic.go:992 +0x71 fp=0xc004d29b20 sp=0xc004d29af0 pc=0x438671
runtime.mapiternext(0xc0d6e87f18?)
runtime/map.go:871 +0x4eb fp=0xc004d29b90 sp=0xc004d29b20 pc=0x41002b
```
time.Format() is not necessary prematurely for JSON
marshalling, since JSON marshalling indeed defaults
to RFC3339Nano.
This also ensures the 'time' is remembered until its
logged and it is the same time when the 'caller'
invoked 'log' functions.
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`
