admin API: change returned HTTP error in hardware info (#8471)
admin API: change returned HTTP error in hardware info (#8471)

This commit replaces the returned error message by
the hardware info handler from `Method-Not-Allowed`
to `Bad-Request` since the current HTTP error is not
correct according to the HTTP spec.

In particular:
```
The origin server MUST generate an Allow header field
in a 405 response containing a list of the target
resource's currently supported methods.
```
From: https://tools.ietf.org/html/rfc7231#section-6.5.5
aead/minio,aead/minio,harshavardhana/minio,donatello/minio,harshavardhana/minio,donatello/minio,fwessels/minio,harshavardhana/minio,NitishT/minio,fwessels/minio,balamurugana/minio,krisis/minio,NitishT/minio,harshavardhana/minio,minio/minio,aead/minio,aead/minio,harshavardhana/minio,harshavardhana/minio,krisis/minio,harshavardhana/minio,minio/minio,NitishT/minio,fwessels/minio,aead/minio,vadmeste/minio,balamurugana/minio,vadmeste/minio,aead/minio,NitishT/minio,aead/minio,aead/minio,harshavardhana/minio,fwessels/minio