Fix bug with no test status updating while standalone run.

Sometimes when single test from testrun is started or restarted its
status is not updated by nose storage plugin. In those conditions
session from nose storage plugin can not access data that were provided
by session of higher level in models.py logic of parent process.
Explicitly closing parent process session before start test running
does help but some additional code modification required in
this case.

Change-Id: Ie5415963c189b66cca58986370982f814f2a7431