[FIX] picking of username for session data directory in case of setuid

Try using geteuid() before getpass.getuser() so a system where
environment user and effective user (e.g. sudo, start-stop-daemon)
creates session-storage directory with a username matching the access
rights.

lp bug: https://launchpad.net/bugs/1172306 fixed

bzr revid: xmo@openerp.com-20130610092107-o4ym83e4ycz450un

addons/web/http.py

@@ -488,9 +488,13 @@ class DisableCacheMiddleware(object):
 
 def session_path():
     try:
-        username = getpass.getuser()
-    except Exception:
-        username = "unknown"
+        import pwd
+        username = pwd.getpwuid(os.geteuid()).pw_name
+    except ImportError:
+        try:
+            username = getpass.getuser()
+        except Exception:
+            username = "unknown"
     path = os.path.join(tempfile.gettempdir(), "oe-sessions-" + username)
     try:
         os.mkdir(path, 0700)