Fix parsing of XML arrays

Previously only the first element of arrays were returned.
Reuse the supervisor proxy object in supervisorctl

supervisorctl was opening 3 connections for a restart command
Lower select timeout

The various deferring classes in http.py would try to delay by 0.1
seconds when data was not yet ready.  However, since the select
timeout was 1 second, we'd end up delaying that long, instead.  This
amounted to each start or stop command taking 1 second to complete.

The comment about the minimum timeout appears to have never been
true.