Create a db_home directory with a unique name so multiple users can

run the test simultaneously.  The simplest thing I found that worked
on both Windows and Unix was to use the PID.  It's unique so should be
sufficient.  This should prevent many of the spurious failures of
the automated tests since they run as different users.

Also cleanup the directory consistenly in the tearDown methods.

It would be nice if someone ensured that the directories are always
created with a consistent name.

Lib/test/test_support.py

@@ -9,6 +9,7 @@ import socket
 import sys
 import os
 import os.path
+import shutil
 import warnings
 import unittest
 
@@ -64,6 +65,14 @@ def unlink(filename):
     except OSError:
         pass
 
+def rmtree(path):
+    try:
+        shutil.rmtree(path)
+    except OSError, e:
+        # Unix returns ENOENT, Windows returns ESRCH.
+        if e.errno not in (errno.ENOENT, errno.ESRCH):
+            raise
+
 def forget(modname):
     '''"Forget" a module was ever imported by removing it from sys.modules and
     deleting any .pyc and .pyo files.'''