Put default bridge into constant.

Reviewed-by: iustinp

lib/constants.py

@@ -84,3 +84,6 @@ INISECT_INS = "instance"
 
 # common exit codes
 EXIT_NOTMASTER = 11
+
+# others
+DEFAULT_BRIDGE = "xen-br0"

scripts/gnt-cluster

@@ -202,15 +202,16 @@ commands = {
                         default="xenvg",),
             make_option("-b", "--bridge", dest="def_bridge",
                         help="Specify the default bridge name (cluster-wide)"
-                        " to connect the instances to [xen-br0]",
+                          " to connect the instances to [%s]" %
+                          constants.DEFAULT_BRIDGE,
                         metavar="BRIDGE",
-                        default="xen-br0",),
+                        default=constants.DEFAULT_BRIDGE,),
             make_option("--master-netdev", dest="master_netdev",
                         help="Specify the node interface (cluster-wide)"
-                        " on which the master IP address will be added "
-                        " [xen-br0]",
+                          " on which the master IP address will be added "
+                          " [%s]" % constants.DEFAULT_BRIDGE,
                         metavar="NETDEV",
-                        default="xen-br0",),
+                        default=constants.DEFAULT_BRIDGE,),
             ],
            "[opts...] <cluster_name>",
            "Initialises a new cluster configuration"),