Use unique build dir for pip installs

There is a bug in pip [1] where it will choose to install a package
from an existing build-dir if it exists over the version actually
requested.

Thus if a prior component has installed a later version of the
package, the unpacked code is already in /tmp/$USER-pip-build; it gets
re-installed and manifests in a confusing error along the lines of

---
 Downloading/unpacking requests>=1.1,<1.2.3
   (from -r /home/stack//python-cinderclient/requirements.txt (line 5))
   Running setup.py egg_info for package requests
   Requested requests>=1.1,<1.2.3 (from -r
   /home/stack/python-cinderclient/requirements.txt (line 5)),
    but installing version 1.2.3
...
  error: Installed distribution requests 1.2.3 conflicts with
    requirement requests>=1.1,<1.2.3
---

I believe pip 1.4 fixes this problem, but it should always be safe to
specify a unique build-directory for pip installs to avoid picking up
old versions.

We also add a cleanup_tmp function for clearing out anything that
stack.sh might leave around when un-stacking, and add a catch-all for
the pip-build dir.

[1] https://github.com/pypa/pip/issues/709

Change-Id: I7ce919cddfd6d6175ae67bd864f82e256ebc7090

functions

@@ -913,14 +913,35 @@ function pip_install {
         PIP_MIRROR_OPT="--use-mirrors"
     fi
 
+    # pip < 1.4 has a bug where it will use an already existing build
+    # directory unconditionally.  Say an earlier component installs
+    # foo v1.1; pip will have built foo's source in
+    # /tmp/$USER-pip-build.  Even if a later component specifies foo <
+    # 1.1, the existing extracted build will be used and cause
+    # confusing errors.  By creating unique build directories we avoid
+    # this problem. See
+    #  https://github.com/pypa/pip/issues/709
+    local pip_build_tmp=$(mktemp --tmpdir -d pip-build.XXXXX)
+
     $SUDO_PIP PIP_DOWNLOAD_CACHE=${PIP_DOWNLOAD_CACHE:-/var/cache/pip} \
         HTTP_PROXY=$http_proxy \
         HTTPS_PROXY=$https_proxy \
         NO_PROXY=$no_proxy \
-        $CMD_PIP install $PIP_MIRROR_OPT $@
+        $CMD_PIP install --build=${pip_build_tmp} \
+        $PIP_MIRROR_OPT $@ \
+        && $SUDO_PIP rm -rf ${pip_build_tmp}
 }
 
 
+# Cleanup anything from /tmp on unstack
+# clean_tmp
+function cleanup_tmp {
+    local tmp_dir=${TMPDIR:-/tmp}
+
+    # see comments in pip_install
+    sudo rm -rf ${tmp_dir}/pip-build.*
+}
+
 # Service wrapper to restart services
 # restart_service service-name
 function restart_service() {

unstack.sh

@@ -111,3 +111,5 @@ if is_service_enabled neutron; then
     stop_neutron_third_party
     cleanup_neutron
 fi
+
+cleanup_tmp