common.sh: Fix test directory with spaces on its name

common.sh

@@ -47,7 +47,7 @@ checkUser()
 # Check whether the output file will be in a existent and writable directory
 checkOutput()
 {
-    local dir="$(dirname $1)"
+    local dir="$(dirname "$1")"
     test -d "$dir" -a -w "$dir"
     return $?
 }