switch_all_submodules_to_head_and_clean: Clean up abandoned worktrees

before adding a new worktree.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit 5b81e0aa93)

switch_all_submodules_to_head_and_clean

@@ -134,6 +134,7 @@ updateModule() {
                   (
                     cd $REPO_LOCALTREE &&
                     git fetch &&
+                    git worktree prune &&
                     git worktree add $PARENTDIR/$MODULE$submodule $branch &&
                     cd $PARENTDIR/$MODULE$submodule &&
                     git branch --set-upstream-to=origin/$branch