More Python package fixes

* Add tools/fixup_stuff.sh to fix prettytable and httplib2 install
  with pip 1.4+
* Cache downloads properly in tools/install_pip.sh

Change-Id: I482590cb91f7a10c1436bc9015afd572ac1cc73e
diff --git a/tools/install_pip.sh b/tools/install_pip.sh
index 0ea8f53..6e3e9d2 100755
--- a/tools/install_pip.sh
+++ b/tools/install_pip.sh
@@ -81,10 +81,12 @@
 }
 
 function install_pip_tarball() {
-    curl -O $PIP_TAR_URL
-    tar xvfz pip-$INSTALL_PIP_VERSION.tar.gz
-    cd pip-$INSTALL_PIP_VERSION
-    sudo python setup.py install
+    (cd $FILES; \
+        curl -O $PIP_TAR_URL; \
+        tar xvfz pip-$INSTALL_PIP_VERSION.tar.gz; \
+        cd pip-$INSTALL_PIP_VERSION; \
+        sudo python setup.py install; \
+    )
 }
 
 # Show starting versions