rgw: implement metadata hander for buckets data

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
armor: don't break lines by default

Added a new function that breaks the lines, but by default
don't do it.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: bucket metadata operations go through metadata handler

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: don't handle ECANCELLED anymore

Simplify, remove obsolete logic.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: metadata handler for bucket set_attr operations

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