rconn: Disable probe for local connections.

rconn: Disable probe for local connections.

There are four sessions established from ovn-controller to the following:
OVN Southbound — JSONRPC based
Local ovsdb — JSONRPC based
Local vswitchd — openflow based from ofctrl
Local vswitchd — openflow based from pinctrl

All of these sessions have their own probe_interval, For the last
two connections, they do not need probe_timer as they are over unix domain
socket. This patch takes care of that.

This change has been tested putting logs in several places like in
ovn-controller.c, lib/rconn.c to make sure the probe_timer is
disabled. Also, by making sure from ovn-controller's
log file that there is no more reconnect happening due to probe
under heavy load.

Signed-off-by: Nirapada Ghosh <nghosh@us.ibm.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>