Add more backup excludes.
Add more backup excludes.

We've seen tar errors for the following files:

Change-Id: Ifc18290ec5e7391dd462fdeb688ca9e00d74daf8
tar: /var/agentx/master: socket ignored
tar: /run/apache2/cgisock.30113: socket ignored
tar: /run/dbus/system_bus_socket: socket ignored

open-switch/infra_puppet-jenkins,open-switch/infra_puppet-jenkins