rgw: handle S3 version 2 pre-signed urls with meta-data

rgw: handle S3 version 2 pre-signed urls with meta-data

Add CanonicalizedAmzHeaders to the v2 signing document, as required
in https://docs.aws.amazon.com/AmazonS3/latest/dev/RESTAuthentication.html

Also lift qs metadata into x_meta_map in RGWPutObj_ObjStore_S3::get_parms(),
so they are applied to the stored object.

Fixes: https://tracker.ceph.com/issues/23470
Signed-off-by: Matt Benjamin <mbenjamin@redhat.com>
(cherry picked from commit 3b0480ed136cebd3fba2322a77c7d047ef6ad5e3)

Conflicts:
	src/rgw/rgw_rest_client.cc
	   - Used 'method()' instead of 'method.c_str()' and
	     'new_url.c_str()' instead of 'url.c_str()'