Set FORMULAS_SALT_MASTER for virtual-mcp11-aio model

After I6c88f51ecbff2199105ab15a96b63bd3af2d5fe0 was merged we need to set
FORMULAS_SALT_MASTER instead of EXTRA_FORMULAS as EXTRA_FORMULAS is overrided
to late.
This patch ensures we set FORMULAS_SALT_MASTER.

Related-PROD: PROD-13339

Change-Id: I9f70eca158349ee6201d853a3b0421e492d5574f
diff --git a/classes/cluster/virtual-mcp11-aio/bootstrap_vars b/classes/cluster/virtual-mcp11-aio/bootstrap_vars
index 3720716..5661577 100644
--- a/classes/cluster/virtual-mcp11-aio/bootstrap_vars
+++ b/classes/cluster/virtual-mcp11-aio/bootstrap_vars
@@ -1 +1 @@
-export EXTRA_FORMULAS="$EXTRA_FORMULAS mysql grafana libvirt rsyslog memcached rabbitmq apache keystone glance nova neutron cinder heat horizon ironic tftpd-hpa bind powerdns designate"
+FORMULAS_SALT_MASTER+=(mysql grafana libvirt rsyslog memcached rabbitmq apache keystone glance nova neutron cinder heat horizon ironic tftpd-hpa bind powerdns designate)