[8.0][Acceptance] Need to increase timeout in mixed_components_murano_sahara_ceilometer

[Dmitry]

Need to increase timeout in mixed_components_murano_sahara_ that consists of the next steps:

1. Create new environment
2. Choose Neutron + TUN, Cinder
3. Enable Sahara, Murano and Ceilometer
4. Add 3 controller, 1 compute, 1 cinder and 3 mongo nodes
5. Verify networks
6. Deploy the environment
7. Verify networks
8. Run OSTF tests

https://github.com/openstack/fuel-qa/blob/stable/8.0/fuelweb_test/tests/tests_os_components/test_mixed_os_components.py#L95

Expected result: OSTF tests should be passed
Actual result: Timeout for OSTF tests is too short

Additional information: Probably new test set should be created and 'tests_platform' should be run there. This separation can help to use the same timeout.