Fixed order of self-update commands

The desirable branch might not be avaiable in the local repository.
Hence, we need to pull first.

scripts/update_stick.sh

@@ -4,5 +4,5 @@ BRANCH="ws14"
 [ -e ".git" ] || exit 1
 [ -z "$1" ] || BRANCH="$1"
 
-git checkout "$BRANCH"
 git pull
+git checkout "$BRANCH"