Fixed OSTF tests for Murano 0.4.1 release.

Removed two extra test cases with deployment of Server Farms,
because Murano uses Neutron Load Balancer for Server Farms and we
have no support of Neutron LB in Mirantis OpenStack.

Also fixed issue with keypairs for linux-based services (it is changed
in Murano and OSTF tests should meet new Murano changes)

Implements blueprint: do-not-use-key-pair-for-murano-ostf-tests

Change-Id: I1066f01e2ff1cc147b217c1bbe1c1d112af06b0f
Merge "Fixed OSTF tests for Murano 0.4.1 release."