[QA] Check horizon performance and limits

[Denis Klepikov]

Please create a performance test for horizon, based on how many concurrent requests it can handle without time lags.

Any horizon user can continuously navigate inside horizon UI, generating 1 click per second.
User should navigate into own tenant with 50% quota usage, create/delete routers, networks, flavors, users, etc. All horizon UI function should be used into this test.

Report should contain follow information:
- numbers of users at the same time (10, 20, 50 , 100, 500);
- horizon pages load (login page, login time, time for all pages);
- numbers of the concurrent requests per second and horizon response time.

[Denis Klepikov (dklepikov)]

Rising priority to high due to many requests from customer side.