Add "make check" dep python-virtualenv in deps.rpm.txt

In fedora20, When 'make  check' and met those error messages:
/src/test/run-cli-tests: virtualenv not installed, skipping python-using
tests.

Signed-off-by: Jianpeng Ma <jianpeng.ma@intel.com>
Merge pull request #3027 from majianpeng/fix1

Add "make check" dep python-virtualenv in deps.rpm.txt

Reviewed-by: Loic Dachary <ldachary@redhat.com>