Pull the SONiC image for all flavors except for the Cumulus flavor (#207

)

Makefile

@@ -87,7 +87,7 @@ partition: partition-bake
 .PHONY: partition-bake
 partition-bake: external_network
 	docker pull $(MINI_LAB_VM_IMAGE)
-ifeq ($(MINI_LAB_FLAVOR),sonic)
+ifneq ($(MINI_LAB_FLAVOR),cumulus)
 	docker pull $(MINI_LAB_SONIC_IMAGE)
 endif
 	@if ! sudo $(CONTAINERLAB) --topo $(LAB_TOPOLOGY) inspect | grep -i leaf01 > /dev/null; then \