RGW/Roles: honor "--max-session-duration" option when CREATING a role

RGW/Roles: honor "--max-session-duration" option when CREATING a role

Currently, this option is not honored and the default (3600s) is used
regardless of whether this option is provided when creating a role:

$ radosgw-admin role create  --role-name=myrole --max-session-duration=43200 ...
$ radosgw-admin role get --role-name=myrole | jq '.MaxSessionDuration'
3600

With this commit, the value given by the --max-session-duration is
considered when creating the role. This would reduce the need for
updating the role's max-session-duration using a separate "role update"
radosgw-admin command call after the role is created:

$ radosgw-admin role create  --role-name=myrole --max-session-duration=43200 ...
$ radosgw-admin role get --role-name=myrole | jq '.MaxSessionDuration'
43200

Signed-off-by: Oguzhan Ozmen <oozmen@bloomberg.net>