get-pip (mininet#1066)

The URL of get-pip.py has changed to https://bootstrap.pypa.io/pip/2.6/get-pip.py

Co-authored-by: lantz <rlantz@cs.stanford.edu>

Author: ramonfontes

util/install.sh

@@ -187,7 +187,7 @@ function mn_deps {
         $install ${PYPKG}-pip || $install ${PYPKG}-pip-whl
         if ! ${PYTHON} -m pip -V; then
             if [ $PYTHON_VERSION == 2 ]; then
-                wget https://bootstrap.pypa.io/2.6/get-pip.py
+                wget https://bootstrap.pypa.io/pip/2.6/get-pip.py
             else
                 wget https://bootstrap.pypa.io/get-pip.py
             fi