rgw: head acls target can be quoted

when passing x-amz-grant-* headers, the target (id, email,
group) may be quoted.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: pass grant headers to target when writeing object

When writing object to remote gateway.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>