webadmin: [Fix] SPICE proxy wrong in Pool

SPICE proxy never shows the Global Configuration value,
if the Cluster configuration value is not defined and
Global Configuration value is defined.

Change-Id: I3272259c2bd33799acf985d86ca6689cba294fe5
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1075222
Signed-off-by: Gustavo Pedrosa <gustavo.pedrosa@eldorado.org.br>