Add a trivial functionaltests/run_tests.sh

I need a simple entry point to running the functional test suite for the
devstack gate job.  This script provides that.  Right now it's quite
trivial and just runs nose.  We'll probably want to update this to testr
later, but it really doesn't matter much right now since there's only a
single test case.

Change-Id: I6cd2ce8d11addf70195e2df2e11161cfd58f04bd
Merge "Add a trivial functionaltests/run_tests.sh"