[build]: Fix docker load image tag not being the expected tag (#12959)

PR #12829 modified the docker tagging scheme such that optional docker
containers would be tagged with the SONiC image version. However, the
docker-image-load macro wasn't updated for these changes. Update it
here.

Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>

slave.mk

@@ -498,11 +498,11 @@ define docker-image-load
     @echo "Obtained docker image lock for $(1) load" $(LOG)
     @echo "Loading docker image $(TARGET_PATH)/$(1).gz" $(LOG)
     docker load -i $(TARGET_PATH)/$(1).gz $(LOG)
-    @echo "Tagging docker image $(1):latest as $(1)-$(DOCKER_USERNAME):$(DOCKER_USERTAG)" $(LOG)
-    docker tag $(1):latest $(1)-$(DOCKER_USERNAME):$(DOCKER_USERTAG) $(LOG)
+    @echo "Tagging docker image $(1):$(call docker-get-tag,$(1)) as $(1)-$(DOCKER_USERNAME):$(DOCKER_USERTAG)" $(LOG)
+    docker tag $(1):$(call docker-get-tag,$(1)) $(1)-$(DOCKER_USERNAME):$(DOCKER_USERTAG) $(LOG)
     if [ x$(SONIC_CONFIG_USE_NATIVE_DOCKERD_FOR_BUILD) == x"y" ]; then
         @echo "Removing docker image $(1):latest" $(LOG)
-        docker rmi -f $(1):latest $(LOG)
+        docker rmi -f $(1):$(call docker-get-tag,$(1)) $(LOG)
     fi
     $(call MOD_UNLOCK,$(1))
     @echo "Released docker image lock for $(1) load" $(LOG)