Misc: Cib model: Only try `booth client list` if @booth[:me] set

If there's a valid booth config file, but none of the listed sites match
an IPaddr2 resource in the CIB, don't bother trying to invoke `booth
client list`, and don't expose the tickets in the booth config file
(this cluster isn't actually part of a geo cluster in this case,
someone's just left a booth.conf lying around).

Signed-off-by: Tim Serong <tserong@suse.com>