Add rgw max attributes constraints

When the swift /info endpoint is queried, Tempest fails checking the
following missing keys:

1. max_meta_count
2. max_meta_name_length
3. max_meta_value_length

Those keys are not present because the related rgw settings are missing,
and as per [1], nothing is generated if the rgw_max_* are not set.
This patch is a workaround, on the TripleO side, to provide the missing
keys to the cluster.

[1] https://github.com/ceph/ceph/blob/master/src/rgw/rgw_rest_swift.cc#L1883-L1900

Closes-Bug: #1950486
Change-Id: I0b199e47cce9dc72490110105f6a4ff94f90934d

deployment/cephadm/ceph-rgw.yaml

@@ -153,6 +153,11 @@ outputs:
                       rgw_swift_versioning_enabled: 'true'
                       rgw_swift_account_in_url: 'true'
                       rgw_trust_forwarded_https: 'true'
+                      # NOTE(fpantano) swift defaults
+                      # https://github.com/openstack/swift/blob/master/swift/common/constraints.py
+                      rgw_max_attr_name_len: 128
+                      rgw_max_attrs_num_in_req: 90
+                      rgw_max_attr_size: 256
 
       metadata_settings:
         if: