testrunner: fixed another mkpath() race with concurrent testrunners
testrunner: fixed another mkpath() race with concurrent testrunners

Commit 15cc5188e98df5b234318d363562f05a5f23acd7 fixed a race condition
in one mkpath(), but mkpath() is used from another place in this script,
and that one was missed.

Change-Id: I99ae2e582296465db4a3be134175bc0fbc39e9cb
Reviewed-by: Kalle Lehtonen <d0f4e666f912516036887a48f8b9d9fc5a6f6350@nokia.com>

tsarajar/qtqa,tsarajar/qtqa,tsarajar/qtqa,tsarajar/qtqa