Revert "Use pip 7 for ironic"

Supposedly pip 8.0.1 fixes this.  Trying a revert to verify.

This reverts commit f068230a5f.

Change-Id: I35b88668bf16ad6205ec678f87e3981aebab32e9

elements/ironic-agent/install.d/ironic-agent-source-install/60-ironic-agent-install

@@ -11,8 +11,7 @@ SCRIPTDIR=$(dirname $0)
 # Install the latest version of pip and setuptools which has some
 # fixes for building behind proxy.
 curl -o /tmp/get-pip.py https://bootstrap.pypa.io/get-pip.py
-#python /tmp/get-pip.py
-pip install pip==7.1.2
+python /tmp/get-pip.py
 rm -f /tmp/get-pip.py
 pip install -U setuptools