Remove pip log copying

We'll change integration.sh to set log=/home/jenkins/pip.log in the
pip.conf file.

Change-Id: Ifac9170d91a67aa7bb8004477dd32b45fdac6b3c
Reviewed-on: https://review.openstack.org/36712
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins