Recent virtualenv review cleanups

This is a follow-on to comments in https://review.openstack.org/156356
and https://review.openstack.org/#/c/151513/

* Remove work-around for /var/cache/pip
* Remove WHEELHOUSE setting in tools/build_wheels.sh and use the pip
  default directory '<cwd>/wheelhouse'
* Remove bogus MySQL-python install
* Removed unused bits and clean up pip commands in from tools/build_venvs.sh

Closes-Bug: #1423720
Change-Id: I0283b0dff9146b1b63bd821358505a93566270c6
diff --git a/files/rpms-suse/devlibs b/files/rpms-suse/devlibs
index dbcd6af..c923825 100644
--- a/files/rpms-suse/devlibs
+++ b/files/rpms-suse/devlibs
@@ -1,6 +1,6 @@
 libffi-devel  # pyOpenSSL
 libopenssl-devel  # pyOpenSSL
 libxml2-devel  # lxml
-libxslt-dev  # lxml
+libxslt-devel  # lxml
 postgresql-devel  # psycopg2
 python-devel  # pyOpenSSL