Fix Cleanup of IceStorm DB Files (#1544)

The 'dbbir' variable was only initialized when 'createDb' is set to true. This resulted in
files being left behind in the IceStorm/persistence test when using two instances, as
shown in the following code snippet:

```python
icestorm1 = IceStorm(createDb=True, cleanDb=False)
icestorm2 = IceStorm(createDb=False, cleanDb=True)
```

scripts/IceStormUtil.py

@@ -27,8 +27,8 @@ def getExe(self, current):
 
     def setup(self, current):
         # Create the database directory
+        self.dbdir = os.path.join(current.testsuite.getPath(), "{0}-{1}.db".format(self.instanceName, self.replica))
         if self.createDb:
-            self.dbdir = os.path.join(current.testsuite.getPath(), "{0}-{1}.db".format(self.instanceName, self.replica))
             if os.path.exists(self.dbdir):
                 shutil.rmtree(self.dbdir)
             os.mkdir(self.dbdir)