Revert "Do not use pip 10 or higher"

This reverts commit f99d1771ba1882dfbb69186212a197edae3ef02c.

Added workarounds that might want to get split into their own patch
before merging:

- Don't install python-psutil
- Don't run peakmem_tracker

Change-Id: If4fb16555e15082a4d97cffdf3cfa608a682997d
diff --git a/tools/install_pip.sh b/tools/install_pip.sh
index 2b6aa4c..dcd5466 100755
--- a/tools/install_pip.sh
+++ b/tools/install_pip.sh
@@ -89,9 +89,9 @@
             die $LINENO "Download of get-pip.py failed"
         touch $LOCAL_PIP.downloaded
     fi
-    sudo -H -E python $LOCAL_PIP -c $TOOLS_DIR/cap-pip.txt
-    if python3_enabled; then
-        sudo -H -E python${PYTHON3_VERSION} $LOCAL_PIP -c $TOOLS_DIR/cap-pip.txt
+    sudo -H -E python${PYTHON3_VERSION} $LOCAL_PIP
+    if ! python3_enabled; then
+        sudo -H -E python $LOCAL_PIP
     fi
 }