Added workaround for steamcmd bug

Steamcmd is unable to download all HLDS files while
doing 'app_update 90'. Updating (unsuccessful) of
apps with IDs 10 and 70 helps by some reason.

Also fixed minor issues in Makefile.

Dockerfile

@@ -15,6 +15,10 @@ RUN mkdir -p /opt/steam && cd /opt/steam && \
 
 # Install HLDS
 RUN mkdir -p /opt/hlds
+# Workaround for "app_update 90" bug, see https://forums.alliedmods.net/showthread.php?p=2518786
+RUN /opt/steam/steamcmd.sh +login $steam_user $steam_password +force_install_dir /opt/hlds +app_update 90 validate +quit
+RUN /opt/steam/steamcmd.sh +login $steam_user $steam_password +force_install_dir /opt/hlds +app_update 70 validate +quit || :
+RUN /opt/steam/steamcmd.sh +login $steam_user $steam_password +force_install_dir /opt/hlds +app_update 10 validate +quit || :
 RUN /opt/steam/steamcmd.sh +login $steam_user $steam_password +force_install_dir /opt/hlds +app_update 90 validate +quit
 RUN mkdir -p ~/.steam && ln -s /opt/hlds ~/.steam/sdk32
 RUN ln -s /opt/steam/ /opt/hlds/steamcmd

Makefile

@@ -1,7 +1,7 @@
 
 # Build options
-IMAGE_NAME="hlds"
-IMAGE_TAG="alpha"
+IMAGE_NAME?="hlds"
+IMAGE_TAG?="alpha"
 
 STEAM_USER?="anonymous"
 STEAM_PASSWORD?=""
@@ -51,4 +51,4 @@ test-clean: test-stop-server
 
 .PHONY: clean
 clean: test-clean
-	docker rmi $(IMAGE_NAME):$(IMAGE_TAG)
+	-docker rmi $(IMAGE_NAME):$(IMAGE_TAG)