VMware: Use multiline for cluster_name opt

cluster_name opt for vSphere driver is MultiStrOpt and currently
users are not able to set multiple values from localrc. This is
fixed by using iniset_multiline function.

Thus, new usage would be :
VMWAREAPI_CLUSTER='cluster1 cluster2 cluster3'
where c1, c2, c3 are the name of the clusters

Change-Id: Ie0f3a48614e6134d849050754932a3613363ce66
diff --git a/lib/nova_plugins/hypervisor-vsphere b/lib/nova_plugins/hypervisor-vsphere
index b04aeda..9933a3c 100644
--- a/lib/nova_plugins/hypervisor-vsphere
+++ b/lib/nova_plugins/hypervisor-vsphere
@@ -39,7 +39,7 @@
     iniset $NOVA_CONF vmware host_ip "$VMWAREAPI_IP"
     iniset $NOVA_CONF vmware host_username "$VMWAREAPI_USER"
     iniset $NOVA_CONF vmware host_password "$VMWAREAPI_PASSWORD"
-    iniset $NOVA_CONF vmware cluster_name "$VMWAREAPI_CLUSTER"
+    iniset_multiline $NOVA_CONF vmware cluster_name "$VMWAREAPI_CLUSTER"
     if is_service_enabled neutron; then
         iniset $NOVA_CONF vmware integration_bridge $OVS_BRIDGE
     fi