Sharing session store between multiple session instances doesn't work

In my code I've two session instances with different cookie options (domain, path). Those two express-session instances share same RedisStore with different cookie options. However it does not seem to matter which express-session instance is used, the later instantiated cookie options will be applied.

To be concrete, I wrote test case to show what I expected the results would be, but currently this test case fails:
```
it('should use own session opts with shared store', function(done){

// The beef: sharing same store instance. Replace with null and the test will pass
var store = new session.MemoryStore()

var app = express()
.use('/path1', createSession({store, cookie: { path: '/path1' }}))
.use('/path2', createSession({store, cookie: { path: '/path2' }}))
.use(function(req, res, next){
res.end()
})

request(app)
.get('/path2')
.expect(shouldSetCookieWithAttributeAndValue('connect.sid', 'Path', '/path2'))
.expect(200, function (err, res) {
if (err) return done(err)
request(app)
.get('/path1')
.expect(shouldSetCookieWithAttributeAndValue('connect.sid', 'Path', '/path1'))
.expect(200, done)
})
})
```

Should it work if one store is shared between multiple session/cookie options? Or is this just wrong usage?