Increase KEYSTONE_LOCKOUT_DURATION to 10

Transient failures were being reported because the current lockout
period for users was too short. While this does increase the
run time IdentityV3UsersTest.test_user_account_lockout, it
allows for more flexibility if there is network latency or some
other factor that cause the lockout to expired before the
next authentication.

Change-Id: I61bc39bbc35ac414b4a72929a90845956c99eb1a
Closes-Bug: 1693917
1 file changed