Add logging to file for OSTF tests

After that change  when performing a OSTF test its result will be
logged to a file under /var/log/ostf directory.
Each file has name in format cluseter_CLUSTER_ID_TESTSET.log,
for example: cluster_1_smoke.log

* added ResultsLogger for logging tests restuts
* removed deprecation because of wrong import in models

Change-Id: If69a4292fcc66565ba969396d591e38eddba92ce
Closes-Bug: #1297958