add timeout for sessions

The default timeout of sessions is 60 minutes.

Set the timeout of sessions 10 minutes explicitly.

Kimchi should have 10 minutes of time out value for the browser login
session.
If session got inactive for 10 minutes then it should expire
automatically.
And should ask user for relogin. This is required for the security
reason.

But this timeout will not take effect on some tabs, such as guest tab.
The root cause is because the front end refreshes the vm list every 5
seconds
by sending the "GET /vms" REST API call to the server.

The follow patch will solve this problem.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
auth enhancement: expire the session when the request access periodically

Now UI will access the vms and host periodically.
That will never make the session expire.
This patch fix this problem.
Now the UI can set "Kimchi-Robot" header when it wants to access the vms
and host periodically.
If the all requests with "Kimchi-Robot" header access for a long time, kimchi
will expire the session.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
UI: set kimchi robot header for some request.

Then session will expire when these request access periodically.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Signed-off-by: Hongliang Wang <hlwang@linux.vnet.ibm.com>
session expire: update test case

update test_config.py.in

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>