Fix pip imports for 10.0.0

Pip 10.0.0 introduced non-backwards compatible changes.  This causes
problem in setup.  Adding handling for different cases.

Issue-ID: DCAEGEN2-452
Change-Id: I06eba2c3d2aa15827a2e66afb37a4c8416810744
Signed-off-by: Lusheng Ji <lji@research.att.com>
diff --git a/python-discovery-client/setup.py b/python-discovery-client/setup.py
index 8648808..5a044ee 100644
--- a/python-discovery-client/setup.py
+++ b/python-discovery-client/setup.py
@@ -18,8 +18,6 @@
 # ECOMP is a trademark and service mark of AT&T Intellectual Property.
 
 from setuptools import setup, find_packages
-from pip.req import parse_requirements
-from pip.download import PipSession
 
 setup(
         name = "onap-dcae-discovery-client",