mod_s2s: Fix logging of <stream:error> consistency with other mods `reason` was often a table, so the log said "table: 0xptr" or such. mod_c2s, mod_bosh etc logs the stream error stanza object, so better do the same. It would be nicer if this was an util.error object, but that will have to be a future change.

-- Only the operators needed by net.websocket.frames are provided at this point
return {
	band   = function (a, b) return a & b end;
	bor    = function (a, b) return a | b end;
	bxor   = function (a, b) return a ~ b end;
};