validate_script.py: add python version to default dev ID
validate_script.py: add python version to default dev ID

Since we run on multiple python versions now and in parallel, we need
to make sure that multiple instances of the test app can run
concurrently.  Use the python version in the device id.  We only run
one session per python version.

Signed-off-by: Paul Barrette <b35f8c7746b911163b905ff32288e207dc9b1bbc@gmail.com>

rcwoolley/device-cloud-python,rcwoolley/device-cloud-python