apk-snap-hook: get rid of redundant logic, pass directly to apk-snap

hooks/apk-snap-hook

 #!/bin/sh
+#passes commit stage (pre/post) to apk-snap
 
-if [ "$1" = "pre-commit" ]; then
-    commit_stage="pre-commit"    
-
-elif [ "$1" = "post-commit" ]; then
-    commit_stage="post-commit"
-fi
-
-/usr/bin/python /usr/bin/apk-snap --ini /etc/apk-snap/apk-snap.ini $commit_stage
+/usr/bin/python /usr/bin/apk-snap --ini /etc/apk-snap/apk-snap.ini $1