install-deps: install setuptools before upgrading virtualenv

install-deps: install setuptools before upgrading virtualenv

this should address the failures when running install-deps.sh, like

Downloading/unpacking virtualenv
  Running setup.py egg_info for package virtualenv
    /usr/lib64/python2.7/distutils/dist.py:267: UserWarning: Unknown
distribution option: 'python_requires'
      warnings.warn(msg)
    error in virtualenv setup command: 'extras_require' must be a
dictionary whose values are strings or lists of strings containing valid
project/version requirement specifiers.
    Complete output from command python setup.py egg_info:
    /usr/lib64/python2.7/distutils/dist.py:267: UserWarning: Unknown
distribution option: 'python_requires'

  warnings.warn(msg)

error in virtualenv setup command: 'extras_require' must be a dictionary
whose values are strings or lists of strings containing valid
project/version requirement specifiers.

this only happens on very old virtualenv shipped with RHEL7.4

Signed-off-by: Kefu Chai <kchai@redhat.com>