tests: avoid reliance on nullglob

Some shells do not have a nullglob feature, including dash (default
/bin/sh on Ubuntu) and the Almquist shell (default /bin/sh on
FreeBSD).  An mv(1) command in setup_dir is failing due to a glob
not matching anything, so use a more widely supported construction.

test/fast/setup_dir

@@ -5,8 +5,9 @@
 
   # Back up
 
-  type setopt >/dev/null 2>&1 && setopt NULL_GLOB
-  type shopt >/dev/null 2>&1 && shopt -s nullglob
   mkdir -p bak
-  mv v* src alias bak || sleep 0s
+  for SRC in v* src alias; do
+    [ -e "$SRC" ] && mv "$SRC" bak
+  done
+  true
 )