Add fudge factor for C++ tests

Occasionally the C++ tests on Jenkins jobs that run on all
build agents aborted because of a timeout which caused the build
to fail. This change makes use of the timeoutFudgeFactor property
that got introduced for the managed tests in commit c4eeb3.

Change-Id: I0d2b21f49f01d573f7abaec0771c7db13a8c7d04