Increase memory for stable/train

CI started showing KP on the redfish job.

Change-Id: Ib429ac90366b9a11e7beca2a068c3eebed8a3638

.zuul.yaml

@@ -43,7 +43,7 @@
         IRONIC_VM_COUNT: 1
         IRONIC_VM_EPHEMERAL_DISK: 1
         IRONIC_VM_LOG_DIR: '{{ devstack_base_dir }}/ironic-bm-logs'
-        IRONIC_VM_SPECS_RAM: 384
+        IRONIC_VM_SPECS_RAM: 512
         IRONIC_VM_SPECS_DISK: 4
         IRONIC_DEFAULT_DEPLOY_INTERFACE: iscsi
         Q_AGENT: openvswitch