Add venv wrapper for check_uptodate.sh

tools/conf/check_uptodate.sh is added in run_tests.sh

For simple, run "run_tests.sh -p" will call it, and get following error:

Failed to collect options from module
cinder.volume.drivers.san.hp.hp_3par_common: No module named hp3parclient

Actually, the hp3parclient is listed in test-requirements.txt, and it is
installed in venv.

the check_uptodate.sh should run in venv to get correct result.

update the error message to update the cindier.conf.sample correctly.

-----------
Test method
-----------
$ pwd
/opt/stack/cinder

$ source .venv/bin/activate; tools/conf/generate_sample.sh

(.venv)$ deactivate

$ ./run_tests.sh  -p
Running flake8 ...
// no error emitted here

Fixes Bug #1219197

Change-Id: I9b3eaf3c1a5eb395eefed28bb907685cdef147aa
Merge "Add venv wrapper for check_uptodate.sh"